JP4664408B2 - Base station method and apparatus for supporting timing synchronization - Google Patents

Abstract

A wireless terminal using OFDM signaling supporting both terrestrial and satellite base station connectivity operates using conventional access probe signaling in a first mode of operation to establish a timing synchronized wireless link with a terrestrial base station. In a second mode of operation, used to establish a timing synchronized wireless link with a satellite base station, a slightly modified access protocol is employed. The round trip signaling time and timing ambiguity between a wireless terminal and a satellite base station is substantially greater than with a terrestrial base station. The modified access protocol uses coding of access probe signals to uniquely identify a superslot index within a beaconslot. The modified protocol uses multiple access probes with different timing offsets to further resolve timing ambiguity and allows the satellite base station access monitoring interval to remain small in duration. Terrestrial base station location/connection information is used to estimate initial timing.

Description

  The present invention relates to a method and apparatus that can be used in implementing an OFDM system that uses OFDM tones to communicate uplink signals to terrestrial and / or satellite base stations.

  The ability to communicate using a handheld communication device (eg, a mobile phone) regardless of the location of a person over a wide area has great utility. The usefulness of such devices is important for military applications as well as conventional consumer-based applications.

  Ground base stations are installed at various earth-based locations to support voice and / or data services. Such base stations typically have a coverage of at most a few miles. Thus, the distance between a conventional cell phone and base station during use is usually only a few miles. Given the relatively short distance between cell phones and terrestrial base stations during normal use, handheld cell phones are usually relatively wide and often have a bandwidth that can support relatively high data rates. In use, for example, on the uplink, with sufficient power to transmit to the base station.

  For one known system based on the use of a terrestrial base station, multiple OFDM tones (eg, in some cases, seven or more tones) are paralleled by a wireless terminal to transmit user data to the base station. Used in. In known systems, user data to be communicated via the uplink and control signals to be communicated via the uplink are usually encoded separately. In known systems, a wireless terminal is for uplink control signaling by an uplink traffic segment corresponding to a tone assigned in response to one or more uplink requests transmitted to a terrestrial base station. A dedicated tone may be assigned. In known systems, uplink traffic channel segment assignment information is broadcast to wireless terminals that monitor assignment signals that can indicate the assignment of uplink traffic channel segments in response to a transmission request. On a recurring basis, the base stations of known systems also broadcast signals that can be used for timing synchronization with timing synchronization signals called beacon signals that repeat over a period of time sometimes called beacon slots.

  Although terrestrial base stations are useful in areas where the population is sufficient to justify the cost of terrestrial base stations, in many places on the planet, there are sufficient commercially valid reasons to deploy base stations It is impractical to deploy fixed terrestrial base stations due to the absence of and / or geographical challenges. In areas that are physically difficult to live, such as open seas, desert areas and / or areas covered by ice sheets, it may be difficult or impractical to deploy and maintain ground base stations. is there.

  The shortage of base stations in some geographic areas results in a “dead zone” where it is impossible to communicate using cell phones. Companies are likely to continue to deploy new base stations to try to eliminate the number of areas where cell phone coverage is lacking, but for the reasons discussed above, in the foreseeable future There is a high possibility that a large earth area in which the effective range of the cell phone from the base station cannot be obtained remains.

  An alternative to ground base stations is to use satellites as base stations. Considering satellite launch costs, satellite base stations are very expensive to deploy. In addition, on the earth, the space where geostationary satellites can be placed is limited. Although satellites in geostationary orbits have the advantage of being in a fixed position relative to the earth, lower earth orbit satellites can be deployed, but such satellites are still expensive to deploy and their initial orbit Is lower than geostationary satellites, so it will stay in orbit for a shorter period of time. Although the distance from the earth's surface on which a mobile phone can be placed to a geosynchronous orbit is substantial (eg, approximately 22,226 miles (35,769 km)), some estimates are 22,300 miles (35,888 km) suggests a better estimate. Adding this to the outlook, the Earth's diameter is approximately 7,926 miles (12,752 km). Unfortunately, for satellite base stations, the distance that the signal must travel is much longer than the distance that the signal travels to reach a conventional ground base station, which is typically a few miles at most.

  As can be appreciated, when considering distance to geostationary orbit, it is often necessary to transmit a signal to the satellite at a higher power level than is required to transmit the signal to the ground base station. . As a result, due to the size of batteries, power amplifiers and other circuits used to implement cell phones, most satellite phones are usually relatively large and bulky compared to conventional cell phones. The need for bulky power amplifiers, which is relatively large, and in many cases, is one reason that many conventional communication systems have peak-to-average power ratios that are less than the ideal peak-to-average power ratio Due to the fact that. A relatively large peak-to-average power ratio is the same average power output, but a larger amplifier is included to support the peak power output that can be used when the peak-to-average power ratio is lower. Request.

  In view of the large distance to the satellite base station and / or the relatively large cell size compared to the terrestrial base station, the uplink timing synchronization used for terrestrial base stations using OFDM signals in the uplink is When communicating with a base station, it may not be sufficient to achieve sufficient uplink symbol timing synchronization. Thus, there is a need for improved methods that support OFDM uplink signaling, including improved timing synchronization methods and / or apparatus that can be used with long round trip delays.

  The present invention relates to a communication method and a communication apparatus suitable for use in a communication system including a remote base station and / or a base station having a larger coverage area.

The method and apparatus of the present invention can be used to synchronize uplink transmission timing of a communication device (eg, wireless terminal) with base station timing. A beacon signal transmitted in the downlink from the base station may be used to facilitate the timing synchronization process. Various beacon signals may be used to support the method and apparatus of the present invention. In some OFDM embodiments, the beacon signal is transmitted in the downlink using one or a few tones for one or a few consecutive periods. In some embodiments, the beacon signal is implemented as a single tone signal that is transmitted for one, two, or three consecutive OFDM symbol transmission periods, depending on the particular embodiment.

  As discussed below, in an OFDM system, transmission of a signal by a communication device to a base station is performed in a synchronized manner thereto (eg, for an OFDM symbol transmitted by a cyclic prefix, a cyclic prefix (cyclic). (prefix) Due to the synchronization level within the period) they should arrive at the base station from which they are transmitted.

  The method and apparatus of the present invention achieves such a synchronization level by various methods and techniques that can be used alone or in combination to achieve the desired synchronization level, even for very remote base stations. To support and make it possible. Much of the discussion within this application focuses on the downlink timing structure and beacon slots that occur in the downlink, but at the base station, the uplink timing has a fixed relationship known as downlink timing. I want you to understand. The received signal and the time at which the signal is received at the base station can be measured in terms of downlink transmission slot and downlink symbol transmission timing while the signal is received in the uplink.

  The uplink timing structure of the present invention, in the meantime, allows access intervals to occur at periodic intervals at which communication devices that are not synchronized with the base station can make access requests in terms of uplink transmission timing. . Such requirements may be contention based. The base station of the present invention monitors for access requests during the access interval and responds with timing corrections and / or other information. Access intervals occur within a known fixed relationship with downlink timing between elements of the uplink timing structure. Each access interval typically has a period that is less than the downlink superslot period in the form of a period.

  A superslot, in various embodiments, each includes multiple OFDM symbol transmission periods (eg, a constant number of OFDM symbol transmission periods). In some embodiments, but not necessarily all embodiments, each uplink superslot includes an access interval. The access interval in the uplink occurs at a fixed relationship location known in relation to the start of the downlink superslot and the beacon signal occurring in the downlink. Thus, the downlink timing structure can be used as a reference for controlling uplink transmission timing as discussed further below.

  Many features of the present invention relate to timing synchronization. Other features of the present invention provide specific access that can be used to register and implement timing synchronization with a remote base station (eg, a base station more than 100 miles (160 km) from the location of the wireless terminal). The present invention relates to a method and an access device.

  In various embodiments, a remote base station is a base station having a minimum distance from a wireless terminal, measured in the form of tens, hundreds, or even thousands of miles during use. A geostationary satellite base station is an example of a remote base station. Geostationary satellite base stations are located thousands of miles above the surface of the earth, and in that case, whatever the minimum distance to communications equipment on the Earth's surface, or even to the communications equipment on civilian planes, Measured in thousands of miles. This may be a terrestrial base station that is located during normal use, for example, within a range of up to 50 miles (80 km) of a wireless terminal, but more typically up to 5 miles (8 km) Contrast with the base station.

  While including the cell phone of the present invention, the method and apparatus of the present invention are well suited for use in communication systems having both terrestrial and satellite base stations, while the method and apparatus of the present invention are fixed. It is very suitable for a wide range of communication applications that require large differences in the amount of output with respect to bandwidth. In the satellite example, the successful uplink signaling for the satellite base station is usually in terms of a fixed bandwidth amount than required for a successful uplink signaling using the same amount of transmission bandwidth for the terrestrial base station. It should be understood that a much larger output amount is required.

  Various functions of the present invention may be used to implement a portable communication device capable of communicating with both remote base stations and relatively close base stations (eg, satellite base stations and terrestrial base stations). A possible method and apparatus. A system implemented in accordance with the present invention may include a plurality of neighboring base stations and remote base stations. In one such system, a terrestrial base station may be used to provide communication coverage with sufficient communication traffic to justify the deployment of the terrestrial base station. Satellite base stations are used to provide fill in coverage in areas where terrestrial base stations are not deployed, for example due to the nature of the physical environment, lack of field for base stations, or other reasons . A portable communication device in an exemplary system can communicate with both a terrestrial base station and a satellite base station, for example, by switching between different operating modes.

  As discussed below, in various embodiments, the system is implemented as an OFDM system. In some embodiments, OFDM signaling is used for uplink signaling as well as downlink signaling. First and second modes of OFDM uplink operation are supported.

During normal operation with the terrestrial base station, the wireless terminal uses multiple tones in parallel in the uplink to simultaneously transmit user data on the multiple tones to the base station. This allows a relatively high data transfer rate to be supported. When operating in multi-tone mode, the average peak-to-average power ratio is a first ratio during the portion of time that user data is transmitted on multiple tones. As discussed below, a second, lower peak-to-average power ratio is achieved, for example, when operating in the single tone mode of operation used for communication with satellite base stations. Thus, when operating in single tone mode, the power amplifier can be used in a more efficient manner. In various embodiments, at the peak-to-average power ratio, the difference between the multi-tone mode of operation and the single-tone mode of operation achieved for a number of symbol time periods is greater than 4 db, typically 6 db is there.

Single tone mode is a method of operating an OFDM wireless terminal to maximize its uplink power budget coverage under typical power constraints encountered when communicating with terrestrial base stations. . This mode is suitable for low rate data on multi-tone channels, ie voice links where ACK is not supported.

In single tone mode, the terminal will transmit on OFDM single tone at once. This tone is represented as a constant logical tone. However, since this tone matches other OFDM channels used in some systems, it is possible to hop from physical tone to physical tone on dwell boundaries, and various implementations This is done in the form. In one embodiment, this logical tone replaces the UL-DCCH channel used to communicate with terrestrial base stations, thereby making it compatible with other OFDM users operating in standard multi-tone mode. maintain.

The content of the single tone uplink channel used by the wireless terminal includes multiplexing of control data and user data in some embodiments. This multiplex may be at the field level within a code word, i.e. some bits from the channel coding block are used to represent control data and the rest represent user data. However, in other embodiments, multiplexing within the single tone uplink channel is codeword level. For example, control data is encoded in a channel coding block, user data is encoded in a channel coding block, and these blocks are multiplexed together for transmission in a single tone uplink channel. Is done. In one embodiment, if the single tone channel is not completely occupied by user data (eg, during silence suppression of voice calls), the transmitter may be blanked during unwanted transmission symbols. Yes, during this period, no signal needs to be transmitted, thereby conserving transmitter power. User data may be multiplexed packet data or regularly scheduled voice data, or a mixture of the two.

For terminals operating in single-tone mode, the downlink acknowledgment signal cannot be transmitted in a separate channel as is done in multi-tone mode, so downlink acknowledgment is a logical single tone up It is multiplexed on the link channel tone or ACK is not used. In such a case, the base station can assume that the downlink traffic channel segment has been successfully received by the wireless terminal explicitly requesting retransmission as needed.

In accordance with the present invention, a wireless terminal operating in a single tone mode can use the standard OFDM component to implement a transmitter while at the same time gaining the transmit power advantage. In standard mode, the transmitted average power typically allows for peak-to-average ratio (PAR) (generally 9 dB) and can cause excessive out-of-band emission. To avoid peak clipping, it is limited to less than the peak power capacity of the transmitter power amplifier. In single tone mode, in various embodiments, the PAR is limited to approximately 3 dB so that the average transmit power can be increased to roughly 6 dB without increasing the probability of clipping.

  The phase of the transmitted waveform can be controlled so that it is a continuous phase across the frequency with frequent hops (changes in the physical tone corresponding to the symbol logical tone occur at the stagnant boundary). . This is because the carrier frequency of the tone is transmitted in the uplink during the cyclic extension of the OFDM symbol so that the signal phase at the end of the symbol is the desired value equal to the start phase of the following symbol. This is possible by changing from one symbol to the next and is implemented in some embodiments, but not necessarily in all embodiments. This continuous phase operation will allow the RAP of the signal to be limited by 3 dB.

OFDM over geostationary satellites is possible with a few modifications of the basic existing basic OFDM communication protocol. Due to the very long round trip time (RTT), there are few or no slaved acknowledge values for the traffic channel. Thus, in some embodiments of the invention, no downlink acknowledgment is sent when operating in single tone uplink mode. In some such embodiments, the downlink acknowledgment is replaced with a retransmission request mechanism in which a request is sent in the UL for retransmission of data that was not successfully received.

  Numerous features, advantages and embodiments of the invention are discussed in the detailed description which follows.

FIG. 1 is a diagram of an exemplary wireless communication system 100 implemented in accordance with and using the method of the present invention. Exemplary system 100 is an exemplary orthogonal frequency division multiplexing (OFDM) multiple access spread spectrum wireless communication system. Exemplary system 100 includes a plurality of base stations (102, 104) and a plurality of wireless terminals (106, 108) (eg, mobile nodes). Various base stations (102, 104) may be coupled together via a backhaul network. Mobile nodes (MN1 106, MN N108) move throughout the system and use the base station where the mobile node is currently located in its coverage area as its network attachment point. It is possible. Some of the base stations are ground-based base stations (eg, BS 102), and some of the base stations are satellite-based base stations (eg, BS 104). From the perspective of the MN (106, 108), terrestrial base stations are considered neighboring base stations (102), while satellite-based base stations are considered remote base stations (104). The MN (106, 108) has two different modes of operation (eg, an uplink multitone mode of operation tailored to power and timing considerations for communication with neighboring (eg, terrestrial) base stations 102, and Including the ability to operate in an uplink single tone mode of operation tailored to power and timing considerations for communication with a remote (eg, satellite) base station 104. In some cases, MN1 106 may be coupled to satellite BS 104 via wireless link 114 and may operate in an uplink single tone mode of operation. In other cases, MN1 106 may be coupled to terrestrial base station 102 via wireless link 110 and may operate in a more conventional multi-tone uplink mode of operation. Similarly, in some cases, the MN N 108 may be coupled to the satellite BS 104 via the radio link 116 and may operate in an uplink single tone mode of operation. In other cases, the MN N 108 may be coupled to the terrestrial base station 102 via the radio link 112 and may operate in a more conventional multi-tone uplink mode of operation.

  Other MNs exist in systems that support communication with one type of base station (eg, terrestrial base station 102) but do not support communication with other types of base stations (eg, satellite base station 104) You can do it.

  FIG. 2 is a diagram of an exemplary base station 200 (eg, a ground-based base station) implemented in accordance with the present invention and using the method of the present invention. The example base station 200 may be a neighboring (eg, terrestrial) base station 102 of the example system 100 of FIG. Since base station 200 provides network connectivity to the WT, base station 200 may be referred to as an access node. Base station 200 includes a receiver 202, a transmitter 204, a processor 206, an I / O interface 208, on which various elements are coupled together via a bus 212 through which data and information can be exchanged. And a memory 210. Receiver 202 includes a decoder 214 for decoding uplink signals received from the WT. Transmitter 204 includes an encoder 216 for encoding downlink signals to be transmitted to the WT. Receiver 202 and transmitter 204 are each coupled to antennas (218, 220) through which uplink signals are received from the WT and downlink signals are transmitted to the WT, respectively. In some embodiments, the same antenna is used for receiver 202 and transmitter 204. I / O interface 208 couples base station 200 to the Internet / other network nodes. Memory 210 includes routines 222 and data / information 224. The processor 206 (eg, CPU) executes the routine 222 and uses the data / information 224 in the memory 210 to control the operation of the base station 200 and perform the method of the present invention. The routine 222 includes a communication routine 226 and a base station control routine 228. Communication routine 226 implements various communication protocols used by base station 200. The base station control routine 228 includes a scheduler module 230 that allocates uplink and downlink segments to the WT, including uplink traffic channel segments, a downlink control module 232, and an uplink multitone user control module 234. Including. The downlink control module 232 includes an automatic retransmission mechanism for downlink traffic channel segments according to the downlink signaling and ack / nak received according to the downlink signaling, including beacon signaling, pilot signaling, assignment signaling, and downlink traffic channel segment signaling. And control. Uplink multi-tone user control module 234 may operate within an assigned uplink traffic channel segment due to operations related to WTs operating in multi-tone uplink mode (eg, access operations) and allocation changes between different WTs over time. Receiving and processing operations for uplink traffic channel user data from WTs communicated simultaneously over multiple (eg, seven) tones, timing synchronization operations, and communication on dedicated control channels using dedicated logical tones Control the control information from the WT being processed.

  The data / information 224 includes a plurality of sets of information (user 1 / MN session A session B data / information 238, user N / MN session X data / data) corresponding to the wireless terminal using the base station 200 as the network connection mechanism point. User data / information 236 including information 240). Such WT user data / information includes, for example, a WT identifier, routing information, segment allocation information, user data / information (eg, voice information, text data packets, video, music, etc.), and an encoded block of information. And may include. Data / information 224 also includes system information 242 including multi-tone UL user frequency / timing / power / tone hopping / coding structure information 244.

  FIG. 2A is a diagram of an exemplary base station 300 (eg, a satellite-based base station) implemented in accordance with the present invention and using the methods of the present invention. Exemplary base station 300 may be BS 104 of exemplary system 100 of FIG. Because the base station provides network connectivity to the WT, the base station 300 may be referred to as an access node. Base station 300 includes a receiver 302, a transmitter 304, a processor 306, and a memory 308 that are coupled together via a bus 310 over which various elements can exchange data and information. Receiver 302 includes a decoder 312 for decoding uplink signals received from the WT. The transmitter 304 includes an encoder 314 for encoding the downlink signal to be transmitted to the WT. Receiver 302 and transmitter 304 are each coupled to an antenna (316, 318) through which an uplink signal is received from a WT and a downlink signal is transmitted to the WT, respectively. In some embodiments, the same antenna is used for receiver 302 and transmitter 304. In addition to communicating with the WT, the base station 300 can communicate with other network nodes (eg, a ground station having a directional antenna and a high capacity link), and the ground station can communicate with other network nodes ( For example, other base stations, routers, AAA servers, home agent nodes, and the Internet). In some embodiments, the same receiver 302, transmitter 304, and / or antenna as previously described with a BS-WT communication link is used for the BS-network node base station link, while others In this embodiment, separate elements are used for different functions. Memory 308 includes routines 320 and data / information 322. The processor 306 (eg, CPU) executes the routine 320 and uses the data / information 322 in the memory 308 to control the operation of the base station 300 and perform the method of the present invention. The memory 308 includes a communication routine 324 and a base station control routine 326. Communication routine 324 implements various communication protocols used by base station 300. The base station control routine 326 assigns a downlink segment to the WT and, in response to the received retransmission request, a scheduler module 328 that reschedules the downlink segment to the WT, a downlink control module 330, A symbol uplink tone user control module 332 and a network module 334 are included. The downlink control module 330 controls downlink signaling to the WT, including beacon signaling, pilot signaling, downlink segment assignment signaling, and downlink traffic channel segment signaling. The symbol UL tone user control module 332 assigns a single dedicated logical tone to the WT user to be used for uplink signaling, including both user data and control information, and uses the BS as its network attachment point An operation including a timing synchronization operation with the WT that is requested to be performed is executed. The network module 334 controls the operation relating to the I / O interface by the ground station link of the network node.

The data / information 322 includes a plurality of sets of information (user 1 / MN session A session B data / information 338, user N / MN session X data / data) corresponding to the wireless terminal using the base station 300 as the network connection mechanism point. User data / information 336 including information 340). Such WT information includes, for example, WT identifiers, routing information, assigned uplink symbol logical tones, downlink segment assignment information, and user data / information (eg, voice information, text data packets, video, music, etc.). And an encoded block of information. Data / information 322 also includes system information 342 including single tone UL user frequency / timing / power / tone hopping / coding structure information 344.

  FIG. 3 is a diagram of an exemplary wireless terminal 400 (eg, mobile node) implemented in accordance with the present invention and using the methods of the present invention. The exemplary WT 400 may be any of the MNs 106, 108 of the exemplary system 100 of FIG. Exemplary wireless terminal 400 includes a receiver 402, a transmitter 404, a processor 406, and a memory 408 that are coupled together via a bus 410 over which various elements can exchange data / information. . Receiver 402 coupled to receive antenna 412 includes a decoder 414 for decoding downlink signals received from the BS. Transmitter 404 coupled to transmit antenna 416 includes an encoder for encoding the uplink signal being transmitted to the BS. In some embodiments, the same antenna is used for receiver 402 and transmitter 404. In some embodiments, an omnidirectional antenna is used.

The transmitter 404 also includes a power amplifier 405. The same power amplifier 405 is used by WT 400 for both multi-tone uplink and single-tone uplink modes of operation. For example, in a multimode uplink mode of operation where an uplink traffic channel segment can typically use 7, 14, or 28 tones simultaneously, the power amplifier can simultaneously receive 28 signals corresponding to 28 tones. There is a need to address peak conditions that are constructively aligned. This tends to limit the average power level. However, when WT 400 operates in the symbol uplink tone mode of operation using the same power amplifier, the concern for constructive synchronization between signals from different tones is not an issue and the average power output level for the amplifier is multi- It can be increased significantly over the tone operating mode. This approach is that according to the present invention, a conventional terrestrial mobile node is adapted with minor modifications and used to communicate uplink signals to a satellite base station at a substantially increased distance. Enable.

Memory 408 includes routine 420 and data / information 422. The processor 406 (eg, CPU) executes the routine 420 and uses the data / information 422 in the memory 408 to control the operation of the wireless terminal 400 and perform the method of the present invention. The routine 420 includes a communication routine 424 and a wireless terminal control routine 426. Communication routine 424 implements various communication protocols used by wireless terminal 400. The wireless terminal control routine 426 includes an initialization module 427, a handoff module 428, an uplink mode exchange control module 430, an uplink single tone mode module 432, an uplink multi-tone mode module 434, and an uplink tone hopping module. 436, an encoding module 438, and a modulation module 440.

The initialization module 427 controls the operation related to the start-up of the wireless terminal (for example, the start-up of the operation from the power-off state to the power-on state) and the operation related to the wireless terminal 400 that requests establishment of a wireless communication link with the base station. To do. The handoff module 428 controls operations related to handoff from one base station to another. For example, WT 400 is currently connected to a terrestrial base station, but can participate in a handoff to a satellite base station. Uplink exchange control module 430 exchanges between different operating modes (eg, when a wireless terminal exchanges communications from a terrestrial base station to a satellite base station, switching from a multi-tone uplink operating mode to a single tone uplink operating mode. ) To control. Uplink single tone mode module 432 includes modules used in a single tone mode of operation for satellite base stations, while UL multitone mode module 434 is used in a multitone mode of operation for terrestrial base stations. Module.

Uplink single tone mode module 432 includes user data transmission control module 422, transmission power control module 444, control signaling module 446, UL single tone determination module 448, control data / user data multiplexing module 450, and DL traffic. A channel retransmission request module 452, a stay boundary and / or intersymbol boundary carrier adjustment module 454, and an access module 456 are included. The user data transmission module 442 controls operations related to uplink user data during the single tone operation mode. The transmit power control module 444 powers to maintain an average peak-to-average power ratio during single-tone uplink mode that is at least 4 dB lower than the peak-to-average power ratio maintained during the multi-tone uplink operation mode. Control transmission of The control signaling module 446 controls signaling during the single tone mode of operation, such control operation being used for uplink control signals transmitted from the WT 400 when the operation switches from multitone mode of operation to single tone mode of operation. Including reducing frequency and / or number. Uplink single tone determination module 448 determines symbol logical tones in the uplink timing structure assigned to the TW to be used for uplink signaling, eg, in association with a base station assigned WT identifier. . Control data / user data multiplexing module 450 multiplexes user data information bits with the control data bits to provide a combined input that can be encoded as a block. The downlink traffic channel retransmission request module 452 may determine that the downlink that has not been successfully decoded if the WT considers the data still valid, for example, considering that there is a greater delay due to the long round trip signaling time. Issue a request to retransmit the traffic channel segment. The dwell boundary carrier adjustment module 454 reduces the carrier frequency of the tone during the cyclic extension of the OFDM symbol ending dwell so that the signal phase at the end of the symbol is the desired value equal to the start phase of the following symbol. Change to Thus, according to the function of some embodiments of the present invention, at the frequency hop, the phase of the transmitted waveform can be controlled to be a continuous phase across the frequency. In some embodiments, frequency adjustment may be performed, for example, for each successive OFDM symbol to provide continuity between successive uplink OFDM symbols transmitted by the WT on the uplink during the symbol UL tone mode of operation. It is executed as part of a multi-part cyclic prefix contained within. This continuity between the symbols of the signal is advantageous in maintaining peak power level control that affects the level at which the power amplifier 405 can be driven during the single tone mode of operation.

  The access module 456 controls operations related to establishing a new radio link with the satellite base station. Such operations include, for example, timing synchronization operations including access probe signaling according to various functions of some embodiments of the present invention. For geostationary satellites with beams that cover a large geographic area, there can be a significant difference in the round trip time between the center and edge of the beam. To resolve this RTT ambiguity, a ranging scheme is used that can resolve a delta RTT of several milliseconds. For example, the timing structure may be divided into different time segments, e.g., superslots, etc., where the superslot represents 114 consecutive OFDM symbol transmission time intervals and different encodings of the access probe signal are for different superslots. May be used. This can be used to allow the timing ambiguity between the WT and the satellite BS to be resolved within the superslot. In addition, repeated access attempts at various time offsets may be repeated (eg, <11.4 milliseconds) to cover superslot ambiguity. In some embodiments, the location for the last detected terrestrial BS may be used to form an initial round trip time estimate (WT-SAT BS-WT), which is generally determined by the terrestrial base station. It is possible to compress the range used within the range supported by the access signaling used for.

  The uplink multitone module 434 includes a user data transmission control module 458, a transmission power control module 460, a control signaling module 462, an uplink traffic channel request module 464, an uplink traffic channel tone set determination module 466, and an uplink A link traffic channel modulation / coding selection module 468, a downlink traffic channel ack / nak module 470, and an access module 472 are included. User data transmission control module 458 includes operations that include controlling transmission of uplink traffic channel segments assigned to the WT.

User data transmission control module 458 controls uplink transmission related operations of user data in a multi-tone mode of operation, where user data is communicated within an uplink traffic channel segment temporarily assigned to the WT, and multiple tones. Including signals that will be transmitted simultaneously. The transmission power control module 460 controls the uplink transmission power level in a multi-tone mode of uplink operation. For example, the output power level is adjusted within the capability range of the power amplifier (eg, not exceeding the peak power output capability of the power amplifier) according to the received base station uplink power control signal. The control signaling module 462 controls power and timing control signaling operations during the multitone uplink operation mode, and the rate of control signaling is higher than the rate of the single tone uplink operation mode. In some embodiments, the control signaling module 462 provides a dedicated control channel provided for the WT by the BS (eg, corresponding to the BS assigned WT identifier) for use in uplink control signaling. Includes the use of logical tones. The control signaling module 462 may encode control information for transmission in the uplink control channel segment that does not include user data. The UL traffic channel request module 464 generates a request for a traffic channel segment to be allocated if, for example, the WT 400 has user data for communication on the uplink. UL traffic channel tone set determination module 466 determines a set of tones for use corresponding to the assigned uplink traffic channel segment. A set of tones includes multiple tones that will be used simultaneously. In multi-tone mode of operation, the logical tone set assigned to a WT to communicate uplink traffic channel user data at some time is different, even though the WT may be assigned the same WT identifier by the same BS. Sometimes it may be different from the logical tones assigned to the WT for communicating uplink traffic channel user data. Module 466 may also use tone hopping information to determine physical tones that correspond to logical tones. The UL traffic channel modulation / coding selection module 468 selects and implements the uplink coding rate and modulation method to be used for the uplink traffic channel segment. For example, in the UL multi-tone mode, the WT may support multiple user data rates implemented using different coding rates and / or different modulation methods (eg, QPSK, QAM16). The DL traffic channel Ack / Nak module 470 controls Ack / Nak decisions and response signaling of received downlink traffic channel segments during the uplink multitone mode of operation. For example, for each downlink traffic channel segment in the downlink timing structure, there may be a corresponding Ack / Nak uplink segment in the uplink timing structure for the UL multitone mode of operation, and the WT is If the downlink traffic channel segment is allocated, for example, an Ack / Nak that conveys the result of transmission is returned to the BS, as used in the automatic retransmission mechanism. The access module 472 controls access operations to establish timing synchronization by establishing an access operation, eg, a nearby (eg, terrestrial) base station, during a multi-tone operation mode. In some embodiments, the multi-tone mode access module 472 has a lower complexity level than the single-tone module access module 456.

Data / information 422 includes uplink operating mode 474, base station identifier 476, base station system information 475, base station assigned wireless terminal identifier 477, user / device / session / resource information 478, uplink User voice data information bits 479, uplink user multiplexed packet data information bits 480, uplink control data information bits 481, a coding block 482 including uplink user data and control data, and a coding user data block When a coded control data block 484, frequency and timing structure information 485, single tone mode coding block information 488, multi-tone mode coding block information 489, single tone mode transmitter blanking (blanking Comprising a reference / information 490, single tone mode transmitter power adjustment information 491, multi-tone mode transmitter power adjustment information 492, and single tone mode carrier frequency / cyclic extension adjustment information 493. Uplink mode of operation 474 is when WT 400 is currently in a multi-tone uplink mode, eg, for communication with a terrestrial base station, or in a single-tone uplink mode, eg, for communication with a satellite base station. Contains information that identifies whether it is present. BS system information 475 includes information related to each of the base stations in the system (eg, base station type (satellite or ground), carrier frequency or frequency used by base station, base station identifier information, sector within base station. , Including timing and frequency uplink and downlink structures used by the base station.

BS identifier 476 includes the identifier of the BS that WT 400 is using as its current network attachment point (e.g., distinguishing the BS from other BSs within the entire system). The BS assigned WT identifier 477 may be an identifier assigned by the BS being used as the network attachment mechanism point of the WT (eg, a value in the range 0 ... 31). In the single tone tone uplink mode of operation, the identifier 477 is associated with a single dedicated logical tone in the uplink timing structure that will be used by the WT for uplink signaling, including both user data and control data. May be. In the multitone uplink mode of operation, identifier 477 may be associated with a logical tone in the uplink timing structure that will be used by the WT for a dedicated control channel for uplink control data. The BS assigned WT identifier 477 can also be used by the BS, for example, when performing segment assignment of uplink traffic channel segments in a multi-tone uplink mode of operation.

User / device session / resource information 478 includes user and device identification information, routing information, security information, ongoing session information, and air link resource information. Uplink user voice data information bits 479 include input user data corresponding to the voice call. Uplink user multiplexed packet data information bits 480 include, for example, input user data corresponding to text, voice, music, data files, and the like. Uplink control data information bit 481 includes power and timing control information that WT 400 desires to communicate to the BS. An encoding block 482 that includes uplink user data and control bits, in some embodiments, is combined with control information bits 481 and / or user information bits 478 and / or 479 formed during the UL single tone mode of operation. Is an encoded output block corresponding to a mixture of The encoded user data block 483 is an encoded block of user information bits 478 and / or 479, while the encoded control data block 484 is an encoded block of control information bits 481. Data and control information is encoded separately in the UL multi-tone mode of operation, and in some embodiments, in the UL single-tone mode of operation. In some embodiments of the single tone mode of operation where the encoding between uplink user data and uplink control data is separate, the ability to blank the transmitter is smooth when there is no user data to communicate. To be. The single tone mode transmitter blanking criteria / information 490 is a number of blanks provided for user data if there is no data to communicate (eg, due to a pause in an ongoing conversation). The output transmitter power is not applied over the symbol uplink tones during that interval). This approach to transmitter blanking results in power savings for the wireless terminal. This is an important consideration when the average power output to facilitate communication with satellites in geostationary orbit is relatively high. In addition, the interference level can be reduced.

Single tone mode coded block information 488 is used for the uplink in a single tone mode of operation (eg, low coding rate using QPSK modulation (eg, supporting at least 4.8 Kbit / s)). Information for identifying the coding rate and the modulation method is included. Multitone mode coding block information 489 may be used to support at least the same coding rate as in single tone mode and a number of additional higher data rates, such as a multitone mode of operation (e.g., It includes multiple different data rate options supported for uplink traffic channel segments in the uplink between various coding rates and QAM4 (eg, modulation schemes including QPSK) and QAM16.

  The frequency and timing structure information 485 includes stay boundary information 486 and tone hopping information 487 corresponding to the BS used as the network connection point. The frequency and timing structure mechanism 485 also includes information identifying logical tones within the timing and frequency structure.

Single-tone mode transmitter power adjustment information 491 and multi-tone mode power adjustment information 492 are respectively the peak power and average power for operation and control of power amplifier 405 in the case of single-tone operation mode and multi-tone operation mode. Information such as peak to average power ratio, maximum power level. Single-tone mode carrier frequency cyclic extension adjustment information 493 is symbol boundaries within the uplink during single-tone operation mode (eg, particularly during hops from one physical tone to another physical tone at a stay boundary). Information used by dwell boundary and / or inter symbol boundary carrier adjustment module 454 to implement continuity between signals.

FIG. 4 is a diagram 500 illustrating exemplary uplink information bit encoding for an exemplary WT (eg, MN) operating in a single tone uplink mode of operation in accordance with various embodiments of the invention. . Within the uplink frequency structure, logical tones are assigned to the WT, for example, directly or indirectly by the base station. For example, the BS assigns a user identifier that may be associated with a specific dedicated logical tone in the single tone mode WT. For example, logical tones are dedicated control channels (DCCH) when the WT is in a multi-tone mode of operation (eg, when the WT typically uses 7 or more tones simultaneously to communicate uplink traffic channel information). ) It may be the same logical tone that is used as the tone. Logical tones may be mapped to physical tones according to tone hopping information known to both the base station and the WT. Tone hopping between different physical tones may occur on a stagnation boundary if the stagnation can be a fixed number (eg, 7) of consecutive OFDM symbol transmission time intervals within the timing structure used in the uplink. . The same logical tone in the uplink frequency structure is used in a single tone mode of operation to convey both control information bits 502 and user data information bits 504. Control information bit 502 may include, for example, power and timing control information. User data bits 504 may include voice user data information bits 506 and / or multiplexed packet user data bits 508. Multiplexer 510 is used to receive control data information bits 502 and user data information bits 504. The output 512 of the multiplexer 510 is an input to an uplink block encoding module 514 that encodes a combination of control information bits and user information bits and outputs an encoded block of encoded bits 516. The coded bits are mapped onto the modulation symbols according to the uplink modulation scheme used (eg, QSPK modulation scheme), and the modulation symbols are transmitted using physical tones that correspond to the assigned logical tones. The uplink rate is such as to support at least one symbol voice call. In some embodiments, the uplink user information rate is at least 4.8 Kbit / s.

  FIG. 5 is a diagram illustrating an exemplary OFDM wireless multiple-access communication system 600 that includes a mix of base stations that are both ground-based and space-based, in accordance with various embodiments of the present invention. Each satellite (satellite 1 602, satellite 2 604, satellite N 606) is a base station (satellite base station 1 608, satellite base station 2 610, satellite base) implemented in accordance with the invention and using the information of the invention. Station N 612). The satellites (602, 604, 608) may be, for example, geostationary satellites that are located in a high earth orbit space 601 around the equator of the Earth 603, approximately 22,300 miles (35,880 km). Each of the satellites (602, 604, 606) may have a corresponding cellular coverage area (cell 1 614, cell 2 616, cell N 618) on the surface of the earth. Exemplary hybrid communication system 600 includes a plurality of terrestrial base stations (terrestrial BS1'620, terrestrial BS2 ') each having a corresponding cellular coverage area (cell 1'626, cell 2'628, cell N'630). 622, terrestrial BSN '624). Different cells or portions of different cells may or may not overlap each other partially or completely. In general, the size of a terrestrial base station cell is smaller than the size of a satellite cell. In general, the number of ground base stations exceeds the number of satellite base stations. In some embodiments, many relatively small terrestrial BS cells are placed in a relatively large cell of the satellite. For example, in some embodiments, terrestrial cells have a typical radius of 1-5 miles (1.6-8 km), while satellite cells generally have a radius of 100-500 miles (160-804 km). There are a plurality of wireless terminals (eg, user communication devices such as cell phones, PDAs, data terminals, etc.) in the system implemented in accordance with the invention and using the method of the invention. The set of wireless terminals may include stationary nodes and mobile nodes, which can move throughout the system. The mobile node can use the base station where the mobile node currently exists in the cell as the network connection point. In some embodiments, if a satellite base station is primarily used to provide access in those areas that are not covered by the ground base station, the ground BS is first accessed by the ground base station or satellite base station. Is used by the WT as an abbreviated type of base station to attempt use at locations where can be provided. For example, in some areas, it is not practical to install ground base stations for economic, environmental, and / or topographic reasons (eg, due to low population density, rugged and difficult to live) There is a case. In some terrestrial base station cells, dead spots may exist due to obstacles such as mountains and high-rise buildings. In such dead spot locations, satellite base stations may be used to fill gaps within the effective range in order to provide the WT user with a more seamless overall effective range. In addition, in some embodiments, priority considerations and user subscribed tier levels are used to determine access to the satellite base station. The base stations are coupled together via, for example, a backhaul network and provide interoperability for MNs located in different cells.

MN communicating with a satellite base station, a single tone, for example, when used for the uplink to support voice channels may operate in single-tone mode of operation. In the downlink, a larger set of tones may be used, eg, 113 downlink tones received and processed by the WT. For example, in the downlink, the WT may be temporarily assigned downlink traffic channel segments that use multiple tones simultaneously as needed. In addition, the WT can receive control signaling simultaneously over different tones. Cell 1 614 includes (MN1 632, MN N634), which communicate with satellite BS1 608 via wireless links (644, 646), respectively. Cell 2 616 includes (MN1′636, MN N′638), which communicate with satellite BS2 610 via wireless links (648, 650), respectively. Cell N618 includes (MN1 ″ 640, MN N′642), which communicate with satellite BS N612 via radio links (652, 654), respectively. In some embodiments, the downlink between the satellite BS and the MN supports a higher user information rate (eg, voice, data, and / or digital video broadcast in the downlink) than the corresponding uplink. Support). In some embodiments, using the satellite BS as its network attachment point, the downlink user data rate provided WT, but approximately the uplink user data rate (eg, 4.8 Kbit / s) Thus, it supports symbol voice calls, but is easy to conserve satellite base station power sources.

  A MN communicating with a terrestrial base station may operate in a conventional mode of operation when multiple tones (eg, 7 or more) are used simultaneously for an uplink traffic channel segment, for example. Cell 1 '626 includes (MN' '' 654, MN N '' '656) communicating with terrestrial BS 1' 620 via wireless links (666, 668), respectively. Cell 2 '628 includes (MN1 "" 658, MN N "" 660) communicating with terrestrial BS2 622 via wireless links (670, 672), respectively. Cell N ′ 630 includes communications (MN 1 ′ ″ ″ 662, MN N ′ ″ ″ 664) that communicate with terrestrial BS N ′ 624 via wireless links (674, 676), respectively.

  FIG. 6 is a diagram illustrating exemplary backhaul interconnectivity between the various satellite-based and ground-based base stations of FIG. Various network nodes (702, 704, 706, 708, 710, 712) support satellites across, for example, routers, home agent nodes, foreign agent nodes, AAA server nodes, and backhaul networks, satellites A satellite tracking / high communication data rate capacity ground station to communicate with. The links (714, 716, 718) between the network nodes (702, 716, 718) functioning as ground stations and the satellite base stations (608, 610, 612) may be radio links using directional antennas. On the other hand, links between terrestrial nodes (720, 722, 724, 726, 728, 730, 732, 734, 736, 738) are wired and / or wireless links (eg, fiber optic cable, broadband cable, microwave link) Etc.).

  FIG. 7A is a diagram 800 illustrating an example satellite 2 604 that includes the example satellite base station 608 and a corresponding cellular coverage area (cell 2) 616 on the surface of the earth. MN 1 636 is located near the center of cell 616 and is closer to satellite 604 than MN N '638 located near the periphery of cell 616. In this example, the beam from the satellite covers a large geographic area, and MN1'636 has a shorter round trip time (RTT), which causes a significant difference in RTT (WT-BS-WT) for two different MNs. Exists. In order to resolve the TRR ambiguity, according to the present invention, a ranging scheme capable of resolving a delta RTT of several milliseconds is implemented.

  In general, in a conventional mode of operation, a WT, which may not be accurately timing synchronized or power controlled, connects to and synchronizes with a base station and uses an uplink tone ( For example, if a request signal can be transmitted on a competition-based uplink tone), there is an access interval built into the timing structure of the system. In accordance with various embodiments of the present invention, additional time-varying coding is used on the access tone set to indicate which forward link superslot is associated with the reverse link transmission, One exemplary scheme for resolving RTT considerations for a single satellite-based tone using access intervals (eg, the same access interval used in a conventional mode of operation). This encoding can be used to resolve ambiguities for the superslot level. For example, a superslot may be approximately 11.4 milliseconds in the form of a period corresponding to 114 consecutive OFDM symbol transmission time intervals. The wireless terminal may need to make an effort to repeat access attempts at various time offsets to cover the superslot (<11.4 milliseconds) ambiguity.

  FIG. 8 is an illustration of an exemplary hybrid system that includes both terrestrial and satellite base stations, and a wireless terminal that utilizes terrestrial base station location information to reduce round trip timing ambiguity with respect to satellite base stations. 800 is shown. An exemplary WT (MNA) 902 has been pre-connected to a terrestrial BS 2 '622 in cell 2'628, but has moved to cell 2 616 covered by satellite BS2. MN A 902 seeks to establish a radio link with BS2 608, but needs to resolve timing ambiguity. In accordance with the functionality of the present invention, the WT includes information associating the location of the terrestrial base station with the satellite base station cell. In some embodiments, multiple terrestrial base stations may be associated with the same satellite cell coverage area (see FIG. 8A). MN A 902 uses information regarding the location of the last detected ground base station 622 to form the initial RTT estimate. Thus, according to the present invention, the ambiguity associated with RTT can be compressed. In some such embodiments, the ambiguity can be compressed within a range supported by the access protocol used with the terrestrial base station.

  FIG. 8A illustrates an exemplary embodiment in which multiple terrestrial base stations are associated with the same satellite base station coverage area according to the present invention. For illustration, three exemplary base stations are shown, although terrestrial BSs generally have a cellular coverage with a radius of approximately 1-5 miles (1.6-8 km) on the surface of the earth. , Since satellites generally have a cellular coverage having a radius of approximately 100-500 miles (160-804 km) on the surface of the Earth, generally within or within the satellite coverage area of a satellite base station Relatedly, it should be understood that there may be more terrestrial base stations. Terrestrial base stations (BS A 956, BS B 958, BS C 960) having corresponding cells (962, 964, 966) are associated with a coverage area (cell D954) corresponding to satellite D950 including satellite BS D952. A wireless terminal that does not know its exact location and seeks to establish a connection with the satellite DBS 952, knows the location information of the location of the ground base station and is known of the satellite base station in geostationary orbit The round trip signal time can be estimated based on the location and, for example, the signaling location for the ground base station, using the known location of the last ground base station to which the WT is connected as a starting point. For example, a terrestrial BS A 956 located near the outer limit of the cell 954 may correspond to an estimate representing the longest RTT and is located at a midpoint between the outer boundary of the cell and the center of the cell. The terrestrial BS B 958 that may represent an intermediate RTT, while the terrestrial BS C 960 located near the center of the cell 954 may represent the shortest RTT.

  FIG. 7 is a flowchart 1200 of an exemplary method of operating a wireless terminal (eg, mobile node) in accordance with the present invention. The wireless terminal may be one of a plurality of first type wireless terminals in an exemplary wireless ODFM multiple access extended spectrum communication system that includes a plurality of base stations, with some base stations on a terrestrial basis. Yes, some base stations are satellite based, and the first type of wireless terminal can communicate with both terrestrial and satellite base stations. An exemplary communication system may include an exemplary second type of wireless terminal that can communicate with terrestrial base stations but cannot communicate with satellite base stations.

Operation of the method of flowchart 1200 begins at step 1202 in response to a powered wireless terminal or in response to a handoff operation. Operation proceeds from start step 1202 to step 1204. In step 1204, the wireless terminal determines whether the network attachment point that the wireless terminal intends to use as the new network attachment point is a terrestrial base station or a satellite base station. If at step 1204 it is determined that the new network attachment point is a terrestrial base station, operation proceeds to step 1206 where the wireless terminal changes its mode of operation to the first mode of operation (eg, multi-tone up). Link operation mode). However, if it is determined at step 1204 that the new network attachment point is a satellite base station, operation proceeds to step 1208 where the wireless terminal changes its mode of operation to a second mode of operation (eg, single Tone uplink operation mode).

  Returning to step 1206, operation proceeds from step 1206 to step 1210, where the WT accepted by the new terrestrial base station receives the base station assigned wireless terminal user identifier. Operation proceeds from step 1210 to steps 1212, 1214, and 1216. At step 1212, the WT is operated to receive a signal corresponding to a downlink traffic channel segment carrying downlink user data from a terrestrial base station. Operation proceeds from step 1212 to step 1218, where the WT transmits an acknowledgment / negative acknowledgment (Ack / Nak) response signal to the base station.

  Returning to step 1214, in step 1214, the WT determines a dedicated control channel logical tone from the WT user ID received in step 1212. Operation proceeds from step 1214 to step 1220. In step 1220, the WT determines a physical tone corresponding to the logical tone for use based on the tone hopping information. For example, a WT assigned ID variable has 32 values (0... 31), each ID corresponding to a different symbolic logical tone in the uplink timing structure (eg, an uplink timing structure containing 113 tones). ). The 113 logical tones may be hopped according to an uplink tone hopping pattern in the uplink timing structure. For example, except for the access interval, the uplink timing structure may be subdivided into a residence interval where each residence interval has a fixed number (eg, 7) periods and a continuous OFDM symbol transmission time interval, and tone hopping is It occurs at the stay boundary but not in the middle. Operation proceeds from step 1220 to step 1222. At step 1222, the WT is operated to transmit an uplink control channel signal using a dedicated control channel tone.

  Returning to step 1216, in step 1216, the WT checks for the presence of user data for transmission on the uplink. If there is no data waiting to be transmitted, operation returns to step 1216 where the WT checks for data to transmit. However, if it is determined at step 1216 that there is user data to transmit on the uplink, operation proceeds from step 1216 to step 1224. In step 1224, the WT requests an uplink traffic channel assignment from the terrestrial base station. Operation proceeds from step 1224 to step 1226. At step 1226, the WT receives an uplink traffic channel segment assignment. Operation proceeds to step 1228, where the WT selects a modulation method (eg, QPSK or QAM16) to use. In step 1230, the WT selects a coding rate to be used. Operation proceeds from step 1230 to step 1232, where the WT encodes user data for the uplink traffic channel segment assigned according to the selected coding rate of step 1230 and according to the selected modulation method of step 1228. Map coded bits to modulation symbol values. Operation proceeds from step 1232 to step 1234, where the WT determines a logical tone to use based on the uplink traffic channel segment assignment. At step 1236, the WT determines a physical tone corresponding to the logical tone for use based on the tone hopping information. Operation proceeds from step 1236 to step 1238. In step 1238, the WT transmits user data to the terrestrial base station using the determined physical tone.

  Returning to step 1208, operation proceeds from step 1208 to step 1240. In step 1240, the WT accepted by the terrestrial base station receives the BS-assigned WT user ID from the satellite base station. Operation proceeds from step 1240 to step 1242 and step 1244.

  At step 1242, the WT is operated to receive a signal corresponding to a downlink traffic channel segment carrying downlink user data from a satellite base station. Operation proceeds from step 1242 to step 1246, where the WT requests transmission of downlink traffic channel user data in response to an error. If the downlink transmission is successfully received and decoded, no response is communicated from the wireless terminal to the base station. In some embodiments, if an error is detected in the information recovery process, for example, the validity time window for lost downlink data will expire before the retransmission can be completed, or data Due to the low priority level, no retransmission request is sent.

  Returning to step 1244, in step 1244, the WT determines a symbol uplink logical tone to use for both control data and user data with respect to the assigned WT user ID. Operation proceeds to step 1248 or step 1250 depending on the particular embodiment.

  At step 1248, the WT multiplexes user data and control data to be communicated on the uplink. The multiplexed data of step 1248 is forwarded to step 1252, where the WT encodes a mixture of user information bits and control information bits into a coded block of symbols. Operation proceeds from step 1252 to step 1254, where the WT determines a physical tone to use for each dwell based on the determined logical tone and tone hopping information. Operation proceeds from step 1254 to step 1256. At step 1256, the WT is operated to transmit a combined block of user data and control data to the satellite base station using the physical tone determined for each dwell.

At step 1250, the WT is operated to encode user data and control data in independent blocks. Operation proceeds from step 1250 to step 1258, where the WT is operated to determine the physical tone to be used for each dwell based on the determined logical tone and tone hopping information. Operation proceeds from step 1258 to step 1260. At step 1260, the WT is operated to transmit an encoded block of user data and control data to the satellite base station using the determined physical tone, determined on a per-dwell basis. With respect to step 1260, according to the functionality of some embodiments of the present invention, if there is no user data to be transmitted during the time interval provided for user data, no single tone is used. Is allowed to finish.

  Operating the wireless terminal according to the method of flowchart 1200 results in multiple times to transmit at least some user data in the first uplink signal having a first peak-to-average power ratio during that time. The wireless terminal will be operated during the first period, including a first plurality of consecutive OFDM symbol transmission periods in a first mode of operation in which OFDM tones are used simultaneously. For example, a WT may be using a terrestrial base station as its network attachment point, and multiple tones (eg, 7, 14, or 28 tones for uplink traffic channel data. ) Can be used simultaneously to communicate uplink user data over air link resources corresponding to uplink traffic channel segments. One or more additional tones (eg, dedicated control channel tones) may be used in parallel for control signaling. Operating the wireless terminal according to the method of flowchart 1200 results in at least a number of times in a second uplink signal having a second peak-to-average power ratio that is different from the first peak-to-average ratio. Wireless terminals during a second period, including a second plurality of consecutive OFDM symbol transmission periods in a second mode of operation in which at most one OFDM tone is used to transmit such user data There is also the possibility of operating. For example, during the second period, the WT may be using a satellite base station as its network attachment point, and an air link resource corresponding to a single dedicated logical tone associated with the base station assigned WT identifier Uplink user data and control data can be communicated above, and the single dedicated logical tone may be hopped to a different physical tone on a stay boundary.

  In some embodiments, the second peak to average power ratio is, for example, at least 4 dB lower than the first peak to average power ratio. In some embodiments, the WT uses an omnidirectional antenna. During the first period, user data communicated on the uplink during the first mode of operation may include user data at a rate of at least 4.8 Kbit / s. During the second period, user data communicated on the uplink during the second mode of operation may include user data at a rate of at least 4.8 Kbit / s. For example, the voice channel may be supported for WT operation in both the first and second modes of operation. In some embodiments, the WT may select a plurality of different uplink coding rate options in the first mode of operation, including a plurality of different coding rates and a plurality of different modulation schemes (eg, QPSK, QAM16). Support. In some embodiments, the WT supports a symbol uplink rate option for operation in a second mode (eg, QPSK) using a single coding rate. In some embodiments, the WT supports a single intimidation uplink rate option for operation in a second mode (eg, QPSK) using a single coding rate. In some embodiments, the information bit rate for the uplink user data signal in the second mode of operation is less than or equal to the minimum information bit rate for the uplink user data signal in the first mode of operation.

  In some embodiments, if a satellite base station is used by the WT as a point of its network connection mechanism, the distance between the satellite base station and the wireless terminal is determined by the WT as a point of the network connection mechanism by the terrestrial base station. When used, it is at least three times the distance between the terrestrial base station and the wireless terminal. In some embodiments, at least some of the satellite base stations in the communication system are geostationary or synchronous orbit satellites. In some such embodiments, the distance between a geostationary or synchronous orbit satellite base station and a WT that uses the satellite base station as its network attachment point is at least 35,000 km, while on the ground The distance between the base station and the WT that uses the ground base station as a point of the network connection mechanism is at most 100 km. In some embodiments, the satellite base station used by the WT as a point of its network attachment mechanism has a cyclic prefix at least with a signal round drip period, each OFDM symbol transmission period corresponding to one OFDM symbol. And leave the WT to exceed 100 OFDM symbol transmission periods, including the amount of time used to transmit.

  In some embodiments, switching from the first mode of operation to the second mode of operation occurs when a handoff occurs between the terrestrial base station and the satellite base station. In some such embodiments where an exchange from the first mode of operation to the second mode of operation occurs, the WT stops sending an acknowledgment signal in response to the received downlink user data. . In some such embodiments where switching from the first mode of operation to the second mode of operation occurs, the WT reduces the frequency and / or the number of uplink control signals transmitted.

  In accordance with various features of the present invention, other embodiments include systems that include space-based base stations but not ground-based base stations, and systems that include ground-based base stations but not space-based base stations. And various combinations including aerial platform based base stations.

  In various embodiments of the present invention, if some communicate with a remote base station that uses multiple tones in the uplink, the UL assignment slave structure is assigned traffic segment> maximum RTT (round trip time). Uplink segment allocation is used by adjusting to account for double. In some cases of terminals that do not necessarily have high gain antennas (eg, handsets with omnidirectional or near omnidirectional antennas), but not necessarily all cases, the success of the signal transmitted by the satellite base station Maximum uplink budget requirements for receiving may limit communication through the use of single mode. Thus, in some embodiments, when a handoff occurs from a terrestrial base station to a satellite base station, the wireless terminal detects the change and switches from a multitone uplink mode to a symbol OFDM tone uplink operational mode.

  For geostationary satellites with a beam that covers a large geographic area, there can be a significant difference in the round trip time between the center and edge of the beam. To resolve this RTT ambiguity, a ranging scheme is used that can resolve a delta RTT of several milliseconds.

  Such a scheme uses existing access intervals in OFDM with additional time-varying coding on the access tone set to indicate which forward link superslot is associated with the reverse link transmission. Can do. This encoding can resolve ambiguity for the superslot level. The terminal may need to make efforts to repeat access attempts at various time offsets to cover the ambiguity of the superslot (<11.4 milliseconds). For hybrid terrestrial-satellite networks, the terminal uses information about the location of the last detected terrestrial base station to form an initial RTT estimate, and the ambiguity is within the range supported by normal access protocols. Can be compressed.

  FIG. 9 is a diagram 1000 illustrating that the round trip signal delay between the satellite base station and the terrestrial WT is greater than the superslot. FIG. 1000 shows a horizontal axis 1002 representing time, an access probe signal 1004 sent from a wireless terminal placed on the ground to the satellite base station, and a response from the satellite base station received by the wireless terminal placed on the ground. Signal 1006. The round trip delay time 1008 is greater than the superslot interval. For example, in some terrestrial wireless communication systems, the access interval is configured once per superslot, providing an opportunity to request that the wireless terminal establish a connection and timing synchronization with a new terrestrial BS. In the case of a ground-based wireless terminal seeking access to a terrestrial base station, if the round trip distance is relatively short (eg, typically 2 to 10 miles (3 to 16 km)), the travel time of the round trip signal is approximately The round trip delay from 11 microseconds to 54 microseconds, including signal processing by the ground base station, may be in a superslot (eg, a time interval of 114 superslots representing approximately 11.4 milliseconds). Therefore, there is no ambiguity as to which superslot the access probe and response signal are associated with. On the other hand, the round trip delay for a terrestrial wireless terminal seeking access to a satellite base station in a synchronous orbit of approximately 22,300 miles (35,880 km) due to the round trip signal travel time of approximately 240 milliseconds Is greater than the superslot interval time of 11.4 milliseconds. In addition, due to the large coverage area of the satellite base station, there may be deviations in the round trip delay, resulting in different RTTs depending on the location of the WT in the cell. According to the present invention, a WT access method that seeks to establish a radio link and timing synchronization with a satellite BS exists when the WT seeks to connect to a satellite BS, and the WT connects to a terrestrial BS. It is modified to address the timing ambiguity issue that does not exist when asked.

  FIG. 10 is a diagram 1100 illustrating one function of the present invention used in the access process to determine timing synchronization between a satellite base station and a WT. FIG. 10 illustrates that the exemplary timing structure is subdivided into superslots (eg, 114 OFDM symbol time intervals), where the start of each superslot is the access interval (eg, 9 OFDM symbol times). Interval). The drawing 1100 includes a horizontal axis 1102 representing time, superslot 1 1104, superslot 2 1106, and superslot N1108. Superslot 1 1104 includes an exemplary ground access interval 1110, Superslot 2 1106 includes an exemplary ground access interval 1112, and Superslot N includes an exemplary ground access interval 1114. A base station may transmit a reference signal (eg, a beacon signal) that defines a beacon slot, and a superslot may be indexed within the beacon slot. In the case of a terrestrial BS, the WT seeking to establish a link with the BS transmits an access probe signal during the access interval, and the BS receiving the signal receives a WT identifier and timing correction to provide synchronization. Can be sent back. However, for satellite BSs, the timing ambiguity is greater than the superslot. Thus, the WT may encode the access signal probe differently depending on which superslot it was transmitted from. The encoded access probe signal 1116 that occurs within the access interval 1110 is encoded to identify superslot 1 1104. The encoded access probe signal 1118 occurring within the access interval 1112 is encoded to identify superslot 2 1106. The encoded access probe signal that occurs within access interval 1114 is encoded to identify superslot N1108. Thus, when the base station receives the encoded access probe signal, the BS can determine from the code the superslot in which the signal was transmitted.

  FIG. 11 is a diagram 1200 illustrating another function of the present invention used in the access process to determine timing synchronization between a satellite base station and a WT. FIG. 11 illustrates that, from a WT perspective, the WT can offset the access probe signal, eg, by a different offset (eg, 400 microsecond offset), so that the satellite can further resolve timing synchronization within the superslot. . Drawing 1200 includes a horizontal axis 1150 representing time, superslot 1 1152, superslot 2 1154, and superslot N1156. Superslots (1152, 1154, 1156) are typically used at the start of each superslot to provide an opportunity for the WT to send access probe signals to the terrestrial base station to establish connection and timing synchronization. Time intervals (1158, 1160, 1162) (eg, nine OFDM symbol transmission time intervals). When operating in a mode to attempt access with a satellite base station, the WT may, relative to the WT criteria, place the access probe at different times in the superslot, including, for example, times outside the interval (1158, 1160, 1162). Can be sent to. A plurality of access probe signals (1164, 1166, 1168) with an exemplary spacing offset between access probe signals of 400 microseconds, illustrating that access probes can occur at various times within a superslot. 1170, 1172, 1174, 1176). An access probe signal (eg, access probe signal (1164, 1166, 1168, 1170, or 1172)) transmitted during superslot 1 1152 is encoded to identify superslot 1. Access probe signals transmitted during superslot 2 1154, such as access probe 1174, are encoded to identify superslot 2. Access probe signals transmitted during superslot N1156, such as access probe signal 1176, are encoded to identify superslot N.

  A terrestrial WT that is not accurately synchronized to a satellite base station and has a large degree of uncertainty due to the large possible distance deviation between the satellite and the WT, is a short interval (eg, The access probe signal from the WT can be monitored for the same interval corresponding to that used by the ground base station). If the transmitted WT probe signal does not hit the window of access interval opportunities for reception within the satellite base station, the satellite base station does not decode the request. The WT can span potential deviations in timing by sending multiple requests with different offsets, and finally the WT probe signal is captured and decoded by the satellite BS. Should be. The satellite BS can then resolve the timing within the superslot by decoding the signal and identifying the superslot from which the signal was directed, and the satellite BS was BS assigned The WT identifier and timing correction signal can be transmitted to the WT. The WT can apply the received timing correction information to synchronize with the satellite base station.

FIG. 12 further illustrates the WT concept of transmitting multiple access probes to a satellite base station with different timing offsets. FIG. 12 is a diagram 1169 including a horizontal axis 1171 representing the time during which the WT transmits a range of access probes to the satellite base station. FIG. 12 shows a first superslot used by the WT to transmit an access probe signal 1175, according to a first timing offset value t ₀ 1179, during which the WT transmits an encoded access probe signal 1177; A second superslot used by the WT to transmit the access probe signal 1180, during which the WT transmits the encoded access probe signal 1182, according to the second timing offset t ₀ + delta 1184, and the N th According to the timing offset value t ₀ + N delta 1190, during which the WT transmits the encoded access probe signal 1188, including the Nth superslot used by the WT to transmit the access probe signal 1186. The satellite BS will accept one of the access probes that happens to fall within the access interval monitored by the BS for accepting and processing the access probe signal from the WT (eg, the kth probe). I want to be.

  For example, consider that the ambiguity in timing between the satellite BS and the terrestrial WT is greater than the superslot. The WT seeks a connection to the satellite BS. The satellite BS outputs a beacon signal, each beacon signal associated with a beacon slot and a set of superslots. Each superslot has an access interval (eg, 9 OFDM symbols) during which the BS accepts coded access probes from the WT seeking to establish a connection with the satellite BS. From the perspective of the BS receiving the signal, if the access probe is outside this access interval window, the BS will not accept the signal. A WT seeking to use a satellite BS as its network attachment point transmits an encoded access probe signal that is encoded to indicate a superslot index. If the WT reaches the BS, the WT's access probe may be out of the acceptance window, so the WT may send multiple probes with different timing offsets, for example with respect to the start of the superslot . For example, a 400 microsecond timing offset may be used. For example, the WT may transmit a sequence of access probes (eg, 10 access probes) approximately every 1/2 second apart, with each successive access probe having a different timing offset with respect to the start of the superslot. Have. However, the BS will only recognize access probe signals received within its access interval window. Access probe signals outside the window are accepted by the system as interference noise. If the BS receives from the WT one of a plurality of access probes received within the access interval window, the BS determines the superslot information by decoding the signal, and the BS and the WT Determine timing corrections to achieve timing synchronization. The BS transmits the WT identifier assigned to the base station, the repetition of the super slot identification information, and the timing correction value to the WT. The WT can receive the base station assigned WT identifier and apply timing correction, thus allowing the WT to use the satellite BS as its network attachment point. A single dedicated logical uplink tone may be associated with an assigned WT identifier for use by the WT for uplink signaling to the satellite BS.

  FIG. 13 is a drawing 1300 illustrating exemplary access signaling according to the method of the present invention. FIG. 13 includes an exemplary base station 1302 and an exemplary wireless terminal 1304, implemented in accordance with the present invention. The example BS 1302 transmits downlink signaling using downlink timing and frequency structure. The downlink timing structure includes beacon slots, each beacon slot includes a fixed number of indexed superslots per beacon slot (eg, 8 indexed superslots), and each superslot is fixed per superslot. A number of OFDM symbol transmission time intervals (eg, 114 OFDM symbol transmission time intervals). Each beacon slot also includes a beacon signal. The downlink signal from BS 1302 is received by WT 1304, and the downlink signaling delay between when BS 1302 transmits and when WT 1304 receives depends on the distance between BS and WT. Received beacon signals 1306 are shown with corresponding beacon slots 1308, including indexed superslots (superslot 1 1310, superslot 2 1312, superslot 3 1314, ..., superslot N1316). WT 1304 may reference uplink signaling for received beacon slot timing.

  BS 1302 also maintains the uplink timing and frequency structure synchronized at the base station with respect to the downlink timing structure. Within the uplink timing and frequency structure range at BS 1302, there is a receive window (eg, one window (1318, 1320, 1322, ..., 1324) corresponding to each superslot) for receiving access signals To do.

  The WT 1304 sends an uplink access probe signal 1326 to the access BS 1302 seeking access to the BS 1302 and registering with the BS 1302. Arrows (1328, 1330, 1332) represent propagation delay cases (A, B) corresponding to (short, medium, and long) distances between BS 1302 and WT 1304, respectively. , C).

  In exemplary case A, WT 1304 successfully sent access probe signal 1326 and successfully hit access opportunity window 1318. The BS 1302 can process the access probe signal to determine the timing offset and send a timing offset correction to the WT 1304, where the WT 1304 is synchronized with the BS 1302 uplink reception timing from the uplink signal from the WT 1304. Allows receiving timing offset correction to be used to adjust uplink transmission timing for the purpose of timing synchronization of its uplink signaling more accurately as it arrives (eg, enables data communication).

  In exemplary case B, WT 1304 failed to hit an access opportunity window (1318, 1320) by sending an access probe signal 1326. BS 1302 does not successfully process the access probe signal, the access probe signal is treated as interference by BS 1302, and BS 1302 does not respond to WT 1304.

  In exemplary case C, WT 1304 successfully sent access probe signal 1326 and successfully hit access opportunity window 1320. The BS 1302 can process the access probe signal to determine the timing offset correction and send the timing offset correction to the WT 1304, where the WT 1304 synchronizes the uplink signal from the WT 1304 with the BS 1302 uplink reception timing. The reception timing offset can be used to adjust the uplink transmission timing for the purpose of timing synchronization of its uplink signaling more accurately (eg, enabling data communication).

  In some embodiments using nearby terrestrial base stations, such as, for example, a terrestrial BS with a cell radius of 5 miles (8 km), the amount of round trip time uncertainty is relatively small and the WT 1304 may Can be expected to hit the next access window at the base station. In some embodiments, if the base station is far from the WT but the relative distance uncertainty is very small, the access probe signal can be expected to hit the access window at the base station.

  However, in embodiments, if the uncertainty in round trip time is greater than that supported by the access interval size, the access probe signal may or may not hit the access opportunity window. In such a case, as in Case B above, if the access probe fails, the WT timing needs to be adjusted and another access probe sent. The access interval window time represents the signaling overhead and it is desirable to keep the access interval short. For example, the exemplary access window time interval is nine OFDM signal transmission time intervals corresponding to an exemplary superslot of 114 OFDM signal transmission time intervals.

  In the example of FIG. 13, consider that the deviation in propagation delay may allow the access probe signal 1326 to hit different access windows 1318, 1320, for example, depending on the relative distance between the WT 1304 and the BS 1302. . For example, Case A (arrow 1328) and Case C (arrow 1332) are such that their relative distance to the WT is such that if the access probe signal is successfully received, the access probe signal is relative to a given time at a given time. Depending on the WT distance, consider corresponding to the same BS, which may differ to the extent that it can be received in a different one of the access windows. Also, consider that the WT will be able to transmit access probe signals during superslots with different index values. In order for the BS to calculate an accurate timing correction, if the BS receives an access probe signal, the base station needs to know more information from the WT 1304 to obtain a timing reference point. According to one feature of some embodiments of the invention, the WT encodes the access probe signal 1326 to identify the superslot index from which the access probe signal 1326 was transmitted. BS 1302 uses the slot index information to calculate the timing offset correction sent to the WT via the downlink signal. The WT 1304 receives the timing correction signal and adjusts its uplink timing accordingly.

  In some embodiments of the present invention, an alternative method is used, in which case the access probe signal does not encode the superslot index, but the base station may communicate with the timing correction signal via the downlink (e.g., access Communicate a slot index offset indicator (which distinguishes between window 1318 and access window 1320). In that case, the WT 1304 knowing the superslot indicator of the transmitted access probe signal combines that information with the received timing correction signal and the received slot indicator indicator to apply the timing adjustment to calculate the decoding timing adjustment. Can do.

  FIG. 14 is a drawing 1400 illustrating exemplary access signaling according to the method of the present invention. FIG. 14 includes an exemplary base station 1402 and an exemplary wireless terminal 1404, implemented in accordance with the present invention. The example BS 1402 transmits downlink signaling using downlink timing and frequency structure. The downlink timing structure includes beacon slots, each beacon slot includes a fixed number of indexed superslots per beacon slot (eg, 8 indexed superslots), and each superslot is defined per superslot. , Including a fixed number of OFDM symbol transmission time intervals (eg, 114 OFDM symbol transmission time intervals). Each beacon slot also includes a beacon signal. Downlink signals from BS 1402 are received by WT 1404, and the downlink signaling delay between when BS 1402 transmits and when WT 1402 receives depends on the distance between BS and WT. Received beacon signal 1406 is shown with a corresponding beacon slot 1408, including indexed superslots (superslot 1 1410, superslot 2 1412, superslot 3 1414, ..., superslot N1416). The WT 1404 may reference uplink signaling regarding received beacon slot timing. The RTT uncertainty is such that when transmitting an access probe signal, the WT 1404 may or may not successfully hit the access slot at the base station 1402.

  BS 1402 also maintains the uplink timing and frequency structure synchronized at the base station with respect to its downlink timing structure. Within the scope of the uplink timing and frequency structure at BS 1402, receive windows for receiving access signals, access slots (eg, one window corresponding to each super slot (1418, 1420, 1422, ..., 1424). )) Exists. In addition, the uplink timing is configured such that there are data slots (1426, 1428, 1428) between access slots.

  FIG. 14 illustrates a method for adjusting an access timing offset with respect to the start of a superslot so that an access probe uplink signal will eventually be received within the access slot range according to the present invention. This method is useful, for example, when deviations in the signal RTT due to potential deviations in the BS-WT distance are not guaranteed to hit the access window on the first attempt.

The WT 1404 transmits an access probe signal 1432 and the transmission timing is controlled so that there is a _first timing offset (timing offset t ₁ 1434) relative to the start of the superslot during which the signal is transmitted. Transmit access probe signal 1432 is an uplink signal that is delayed by signaling propagation as represented by tilt arrow 1433 and arrives at the receiver of BS 1402 as access probe signal 1432 ′. However, the access probe signal 1432 ′ happens to arrive during the data slot 1426 and is therefore considered to be interference by the BS 1402. BS 1402 does not send a response to WT 1404.

The WT 1404 adjusts the timing offset to the second timing offset value t ₂ 1438 and transmits an access probe signal 1436. Transmit access probe signal 1436 is an uplink signal that is delayed by signaling propagation as represented by tilt arrow 1437 and arrives at the BS 1402 receiver as access probe signal 1436 ′. However, this time, the received access probe signal 1436 ′ is within the range of the access slot 1420, and the BS 1402 processes the access signal, accepts the WT 1404 to be registered, calculates the timing correction signal, and goes through the downlink. The timing correction signal is transmitted to the WT 1404. The WT adjusts its uplink timing according to the reception timing correction signal.

  The difference between the access probe signaling timing offsets may be selected in correlation with the size of the access slot so that successive access probes will eventually hit the access slot with different offsets. For example, in an exemplary system having nine OFDM symbol transmission time intervals, the different time offsets may differ by four OFDM symbol transmission time intervals, for example, if the OFDM transmission time interval is approximately 100 microseconds.

  FIG. 15 is a diagram 1500 illustrating exemplary access signaling according to the method of the present invention. FIG. 15 includes an exemplary base station 1502 and an exemplary wireless terminal 1504, implemented in accordance with the present invention. An exemplary BS 1502 is a satellite in geosynchronous orbit having a large cellular coverage area (eg, a radius of 100 miles (160 km), 200 miles (321 km), 500 miles (804 km), or more) on the surface of the earth. I want to be considered BS. In such an embodiment, the RTT is larger than the superslot in the downlink, e.g., due to potential WT 1504 position deviation, the RTT uncertainty can cause the exemplary access probe signal to successfully access time slot at the base station 1500. Think of it as something that might or might not hit. In this exemplary embodiment, the two functions described above are different from encoding the superslot index identification information into the access probe and the beginning of the superslot in which the access signal is transmitted. Sending a continuous access probe with a timing offset is used in combination to obtain a timing correction for WT 1504.

  BS 1502 transmits a downlink signal including a downlink beacon signal for each beacon slot that is part of a downlink timing structure including a superslot, and the downlink timing structure is known to the BS and WT. The WT 1504 may synchronize with respect to the received downlink signal and may identify the superslot index value within each beacon slot.

The WT 1504 determines that the WT 1504 wants to use the BS 1502, ie, the satellite BS, as its network attachment point. However, WT 1504 does not know its location and therefore does not know RTT. The WT 1504 transmits an access probe signal 1508 with a _first timing offset t ₁ 1510 with respect to the start of the superslot 1512 during which the signal is transmitted. The index of superslot 1512 in that beacon slot is known to WT 1504 and is encoded in access probe signal 1508. After the WT-BS propagation delay time, the access signal arrives at BS 1502 as access probe 1508 ′. However, the access probe signal 1508 ′ hits the data slot 1514, not the access slot. BS 1502 treats signal 1508 ′ as interference and does not respond to WT 1504.

  The wireless terminal 1504 waits for a time interval 1516 before sending another access probe signal. The time interval 1516 is selected to be greater than RTT plus some additional time allowed for signal processing, the access probe signal successfully hits the access slot at BS 1502, and BS 1502 registers If a WT 1504 is accepted, a BS 1502 access probe response signal is generated, transmitted, propagated, and provides sufficient time to be detected by the WT 1504.

  If a response is not received within the predicted time interval, the WT 1504 adjusts its timing offset from the beginning of the superslot to a second timing offset 1518 that is different from the first timing offset 1510, between the superslots 1522. Another access probe signal 1520 is transmitted. The index of superslot 1522 in that beacon slot is encoded in signal 1520 and the index value may be the same as or different from the index value encoded in signal 1508. After the WT-BS propagation delay time, the access signal arrives at BS 1502 as access probe 1520 '. In this case, the access probe signal 1520 ′ hits the access slot 1521. BS 1502 decodes the communicated superslot indicator, measures the timing offset of received signal 1520 ′ in access slot 1512, and uses the measured timing offset and superslot information to calculate a timing correction value for WT 1504. use. BS 1502 transmits a timing offset correction value to WT 1504 as a downlink signal. The WT 1504 receives and decodes the timing offset value and adjusts its uplink timing according to the received correction. WT 1504 provides signaling identifying that WT 1504 has been accepted for registration by BS 1502 prior to the time it will attempt to send another access probe signal, eg, using another offset. Recieved.

  FIG. 16 is a flowchart 1600 of an exemplary method of operation for a wireless terminal to connect to a base station and perform a timing synchronization operation in accordance with the present invention. Operation starts in step 1602, where the WT is powered and initialized and begins receiving downlink signals from one or more base stations. Operation proceeds from step 1602 to step 1604.

  In step 1604, the WT determines whether to seek access to the satellite base station or to initiate access to the ground base station. An exemplary WT implemented in accordance with the present invention may include different access method implementations. The first access method is tailored for satellite base stations, for example, satellite base stations in geosynchronous orbits having a cell coverage area on the surface of the earth having a radius of approximately 100-500 miles (160-804 km). In this case, the signal RTT is larger than the superslot, and the ambiguity in the RTT is larger than the access time interval. The second access method is tailored to a terrestrial base station having, for example, a relatively small cell radius (eg, 1 mile (1 km), 2 mile (3 km), or 5 mile (8 km)), where The signal RTT is less than a superslot and the ambiguity in the RTT is sufficient so that the access request signal sent from the WT should be expected to hit the access slot at the terrestrial BS in a single attempt. small. If the WT seeks access to the satellite BS, operation proceeds from step 1604 to step 1606, while if the WT seeks access to a terrestrial base station, operation proceeds from step 1604 to step 1608.

  In step 1606, the WT is operated to receive a downlink beacon signal or a signal from the satellite BS. The downlink timing and frequency structure used by the satellite base station in the exemplary system may include beacon slots that occur on a repetitive basis, each beacon slot includes a beacon signal, and each beacon slot is a fixed number of superslots. (E.g., 8), each superslot within a beacon slot is associated with an index value, and each superslot includes a fixed number of OFDM symbol transmission time intervals (e.g., 114).

  Operation proceeds from step 1606 to step 1608. At step 1608, the WT determines a timing reference from the received beacon signal (s) (eg, determines the start of a beacon slot for received downlink signaling). At step 1610, the WT sets the probe counter equal to 1, and at step 1612, the WT sets the timing offset variable equal to the initial timing offset. For example, the initial timing offset is a predetermined value stored in the WT. Operation proceeds from step 1612 to step 1614.

  In step 1614, the WT selects a superslot within the beacon slot to transmit the first access probe signal and identifies an indicator of the selected superslot. Then, at step 1614, the WT encodes the selected superslot in the first access probe signal. Next, in step 1618, the WT receives the first access at the time point that occurs in the selected superslot so that the transmission is timing off from the start of the superslot selected by the timing offset value in step 1612. Send a probe signal. Operation proceeds from step 1618 to step 1622 via connection node A 1620.

  At step 1622, the WT is operated to receive downlink signaling from the satellite base station, and the received downlink signaling may include a response to the access probe signal. Operation proceeds from step 1622 to step 1624. At step 1624, the WT checks whether a response has been received towards the WT. If no response is received, operation proceeds from step 1624 to step 1626. However, if a response is received towards the WT, the WT operation proceeds to step 1628.

  At step 1626, the WT checks to see if the change in time since the last access probe transmission exceeds the predicted worst RTT + processing time (eg, a predetermined limit value stored in the WT). If the deadline has not been exceeded, operation returns to step 1622 where the WT continues to receive downlink signals and check for responses. However, if at step 1626 it is determined that the WT has exceeded the deadline, the WT operation proceeds to step 1630 where the WT increments the probe counter.

  Next, at step 1632, the WT checks whether the probe counter exceeds the maximum number of probe counters. The maximum probe counter number should be expected to be timed due to different timing offsets so that at least one of the access probes hits an access slot at least one of the access probes. As is, it may be a predetermined value stored in the WT memory that is selected to be sufficient to cover timing ambiguity.

  If the probe counter exceeds the maximum number of probes at step 1632, it can be estimated that the access attempt set resulted in failure and operation proceeds to step 1604 via connection node B 1634. For example, possible causes of failure are due to interference conditions such as loading conditions where the access probe signal that should have hit the access slot at the base station could not be successfully detected and processed, It may include an interference condition where the satellite BS has decided to refuse WT access, or an interference condition where the response signal from the satellite base station could not be successfully recovered. At step 1604, the WT may determine whether to repeat the process with the same satellite base station or attempt to access a different base station.

  If, at step 1632, the probe counter does not exceed the maximum number of probe counters, operation proceeds to step 1636, where the WT sets the timing offset equal to the current timing offset value plus the delta offset. For example, the delta offset may be a fraction of the access slot interval (eg, less than half). Then, at step 1640, the WT selects a superslot within the beacon slot to transmit another access probe signal to identify the indicator of the selected superslot. Next, at step 1642, the WT encodes the indicator of the selected superslot in another access probe signal. Then, in step 1644, the WT receives another access at the time point that occurs in the selected superslot so that the transmission is timing off from the start of the superslot selected by the timing offset value in step 1638. Send a probe signal. Operation returns from step 1644 to step 1622 via connection node A 1620, where the WT receives the downlink signal and examines the response to the access probe signal.

  Returning to step 1624, if it is determined in step 1624 that the WT has received a response addressed to the wireless terminal, operation proceeds to step 1628, where the WT includes the timing correction information and returns to the WT. Process the directed incoming response. Operation proceeds from step 1628 to step 1646. In step 1646, the WT adjusts the WT timing according to the reception timing correction information.

  Returning to step 1604, if, in step 1604, the wireless terminal seeks to initiate access via the terrestrial BS station, operation proceeds to step 1608, where the WT is one or more from the terrestrial base station. Operated to receive the downlink beacon signal, the WT wishes to use it as its network attachment point. Next, at step 1646, the WT determines a timing reference from one or more received beacon signals, and at step 1648, the WT is predicted that an access request signal is received at the terrestrial base station during the access period. As it should, the determined time reference is used to determine when the access request signal should be transmitted. Operation proceeds from step 1648 to step 1650.

  In step 1650, the WT is operated to transmit an access request signal such that the access request signal is at a predetermined time, wherein the access request signal does not include encoded superslot identification information. Next, in step 1652, the WT is operated to receive downlink signaling from the terrestrial BS that may include access grant information. Operation proceeds from step 1652 to step 1654.

  At step 1654, the WT is operated to determine whether the WT has received an access grant signal in response to its access request transmission. If an access grant is not received, operation proceeds to step 1654 via connecting Node B 1634, where the WT determines whether to try again with the same terrestrial base station or with a different BS. decide. If it is determined in step 1654 that the WT has been granted access to use the terrestrial BS as its network attachment point, operation proceeds to step 1656 where the WT includes timing correction information, Operated to process access grant signaling directed to the WT. Then, in step 1658, the WT is operated to adjust the WT timing according to the reception timing correction information in step 1656.

  FIG. 17, including the combination of FIG. 17A and FIG. 17B, is a flowchart 1700 of an exemplary method of operating a communication device for use in a communication system. For example, the exemplary communication device may be a wireless terminal, such as a mobile node, implemented in accordance with the present invention, and the exemplary communication system may be a multiple access extended spectrum OFDM wireless communication system. The communication system includes one or more base stations, each base station capable of transmitting a downlink beacon signal. Various base stations in the system may or may not be timing synchronized with each other. In an exemplary communication system, a beacon signaling broadcast by a base station can be used in providing timing reference information for the base station. In the exemplary communication system, the timing structure for the base station is such that beacon time slots occur on a periodic basis, and the beacon signal is transmitted by the base station during each beacon time slot according to a periodic downlink timing structure. The downlink timing structure includes a plurality of superslots in each beacon slot, and each superslot in each beacon slot is suitable for identification by use of a superslot index, and each superslot has a plurality of superslots. Signal transmission period.

  Operation begins in step 1702, where the communication device is powered and initialized. Operation proceeds from step 1702 to step 1704. In step 1704, the communication device receives at least one beacon signal from a base station (eg, satellite BS) that the communication device desires to use the network attachment point. In some embodiments, the communication device receives multiple beacon signals and / or other downlink broadcast information (eg, pilot signals) from the base station before proceeding. Operation proceeds from step 1704 to step 1706. In step 1706, the communication device processes the received beacon signal to determine a downlink timing reference point, and a superslot is generated in a beacon slot having a predetermined reference relative to the determined timing reference point. Operation proceeds from step 1706 to step 1708.

  In step 1708, the communication device determines a time for transmitting the first access probe according to the determined timing reference point. For example, the first access probe has an initial time offset from the determined timing reference point. In some embodiments (eg, some hybrid systems including both satellite and terrestrial base stations), the communication device performs sub-step 1709, where the communication device is from the terrestrial base station. The time for transmitting the first access probe is determined in accordance with the position information determined from the first signal. In some such embodiments, determining the time to transmit the first access probe is further performed in response to known information indicating the location of the ground base station and the location of the satellite base station. The For example, the base station to which the communication device currently wishes to transmit an access probe signal may be a satellite base station, which is relatively large in the signal RTT due to a large coverage area on the surface of the earth. Due to the deviation, there may be a relatively large amount of uncertainty in the timing for use in transmitting the access probe and the current location of the communication device may not be known. However, the satellite cell coverage area may include overlapping with several smaller cells and / or being near these cells, with these smaller cells corresponding to terrestrial base stations. By determining an approximation of the current position of the communication device determined from the terrestrial base station signal, the communication device can reduce timing uncertainty about when to transmit the access probe, thereby allowing access. It increases the likelihood that the probe will be accepted by the satellite base station and reduces the time and number of different timing offset access probes that need to be transmitted to the satellite BS. For example, a communication device has stored information that identifies the last terrestrial BS where the communication device was used as an access point and the location of a known terrestrial BS stored in the communication device. Information that correlates terrestrial BS cells to satellite positions and / or satellite cell positions may also be stored and used. In some embodiments, the communication device can triangulate its location based on beacon signals received from multiple ground base stations. In some embodiments, the location information obtained from a terrestrial base station is used so that the first access probe signal for a satellite base station should be expected to hit the access slot of that satellite base station. By doing so, it may be possible to reduce the level of timing uncertainty.

  Operation proceeds from step 1708 to step 1710. At step 1710, the communication device encodes information in the first access probe signal that identifies the first superslot index. Then, in step 1712, the communication device transmits a first access probe signal that identifies the first superslot indicator, the first access probe signal being associated with the start of the first superslot indicator. 1 is transmitted at a timing offset. Operation proceeds from step 1712 to step 1714, where the communications device monitors to determine whether a response to the first access probe signal has been received from the base station. Then, in step 1716, operation proceeds to step 1718 if no response is received, and proceeds to step 1720 if a response is received.

  If a response is received, at step 1720, the communication device performs transmission timing adjustments according to the information included in the response.

  However, if no response is received, at step 1718, the communications device encodes information in the second access probe signal that identifies the second superslot indicator, and at step 1722, the communications device Transmitting a second access probe signal identifying a superslot index at a second timing offset associated with the start of a second superslot having the second superslot index, wherein the second timing offset is 1 timing offset. Operation proceeds from step 1722 to step 1726 via connection node A 1724.

  In step 1726, the communications device monitors to determine whether a response to the second access probe signal has been received from the base station. Then, in step 1728, operation proceeds to step 1732 if no response is received, and proceeds to step 1730 if a response is received.

  If a response is received, at step 1732 the communication device performs transmission timing adjustment according to the information contained in the response.

  However, if no response is received, at step 1730, the communication device encodes information in the third access probe signal identifying the third superslot indicator, and at step 1734, the communication device Are transmitted at a third timing offset in relation to the start of a third superslot having the third superslot index. The third timing offset is different from the first and second timing offsets.

  Operation proceeds from step 1734 to step 1736. In step 1736, the communications device monitors to determine whether a response to the third access probe signal has been received from the base station. Then, in step 1740, operation proceeds to step 1742 if no response is received, and proceeds to step 1740 if a response is received.

  If a response is received, at step 1742, the communication device performs transmission timing adjustment according to the information included in the response. If no response is received at step 1740, the communication device continues the process of access signal generation / transmission / response determination / further operation according to the embodiment. For example, in some embodiments, the communication device communicates access probes with different timing offsets for each successive access probe until the probe is answered or a fixed number of access probes are transmitted. Is possible. For example, the total number of access probes may be sufficient to cover at least the expected timing ambiguity.

  In some embodiments, the first and second access probes are transmitted in different beacon slots, and the second superslot index may be the same as or different from the first superslot index. . In some embodiments, the first and second access probes are transmitted in different beacon slots, and the second superslot index is different from the first superslot index.

  In some embodiments, the first and second access probes are transmitted in the same beacon slot, and the second superslot is different from the first superslot. In some such embodiments, the response includes information identifying one of the probe signals being responded.

  In some embodiments, when a sequence including at least three access probes is transmitted, the second timing offset is the first timing offset value plus a first integer multiple of a fixed step size offset. Unlike the timing offset, the third timing offset is the first timing offset value that is different from the first integer multiple of the fixed step size offset and the second integer multiple of the fixed step size timing offset. Different from timing offset. In some embodiments, the first and second integer multiples of the fixed step size timing offset may be positive numbers or negative numbers.

  In some embodiments, the fixed step size is less than the period of the base station access interval, and the base station access interval is the period during which the base station corresponds to the access probe signal.

  In various embodiments, the base station to which the communication device transmits an access probe is a satellite base station, and the round trip time (RTT) of the light traveling signal between the satellite base station and the communication device. Exceeds the superslot period. In some such embodiments, the RTT also exceeds the duration of the beacon slot. In some embodiments, the RTT is greater than 0.2 seconds.

  FIG. 18 is a flowchart 1800 of an exemplary method of operating an exemplary communication device in accordance with the present invention. The exemplary method of flowchart 1800 illustrates that beacon time slots occur on a periodic basis, and that a beacon signal is transmitted by the base station during each beacon time slot according to a periodic downlink timing structure, wherein the downlink timing structure is For use in a communication system that includes multiple superslots within a beacon slot, each superslot within the beacon slot is suitable for identification by use of a superslot indicator, and each superslot includes multiple symbol transmission periods Is an operation method of the communication apparatus.

  Operation begins in step 1802, where the communication device is powered and initialized. Operation proceeds from step 1802 to step 1804, where the communication device is operated to receive at least one beacon signal, and then in step 1806, the communication device receives to determine a downlink timing reference point. Processing beacon signals, superslots occur within beacon slots that have a predetermined relationship with a predetermined timing reference point. Operation proceeds from step 1806 to step 1808.

  In step 1808, the communication device encodes an access probe identifier in at least one of the first and second access probes. In step 1810, the communication device transmits a first access probe at a time corresponding to a first timing offset in relation to the start of a superslot in a beacon slot. Then, in step 1812, the communication device transmits a second access probe at a time corresponding to the second timing offset in relation to the start of the superslot, wherein the second access probe is less than the larger superslot period. From the time point at which the first access probe is transmitted, the transmission signal is transmitted at a time point that is twice the time required to move from the communication device to the base station. Operation proceeds from step 1812 to step 1814.

  At step 1814, the communication device is operated to monitor to determine whether a response has been received from the base station, and at step 1816, operation proceeds in response to the determination. If a response is received from the base station, operation proceeds from step 1816 to step 1818. In step 1818, the communication device performs transmission timing adjustment according to the information included in the response. If no response is received from the base station, operation proceeds from step 1816 to step 1804 via connection node A 1820, where the communication device can resume the process of initiating access signaling.

  In some embodiments, the maximum timing ambiguity is less than the duration of the superslot, and the time between transmissions of the first and second access probes is less than the duration of the superslot. In some embodiments, the first and second access probes are transmitted from each other at intervals less than or equal to the access interval during which the base station will respond to the received access probes.

  In various embodiments, where the received response includes information identifying the access probe to which the response corresponds, performing the transmission timing adjustment in response to the information included in the response includes timing correction information received from the base station. And determining the amount of timing adjustment to be performed from information relating to the transmission time of the probe identified in relation to the determined downlink timing reference point.

  FIG. 19 is a flowchart 1900 of an exemplary method of operating an exemplary communication device in accordance with the present invention. The exemplary method of flowchart 1900 includes a beacon time slot occurring on a periodic basis and a beacon signal transmitted by a base station (eg, a satellite base station) during each beacon time slot according to a periodic downlink timing structure; The downlink timing structure includes a plurality of superslots within each beacon slot, each superslot within the beacon slot is suitable for identification by use of a superslot indicator, and each superslot includes a plurality of symbol transmission periods A method for operating a communication device for use in a communication system (eg, an OFDM system).

  Operation begins in step 1902 where the communication device is powered and initialized. Operation proceeds from step 1902 to step 1904, where the communication device is operated to receive at least one beacon signal from the base station, and then in step 1906, the communication device determines a download timing reference point. The received beacon signal is processed, and a superslot is generated in a beacon slot having a predetermined relationship with the determined timing reference point. Operation proceeds from step 1906 to step 1908.

  In step 1908, the communication device is operated to transmit an access probe signal to the base station. Then, in step 1910, the communication device receives a response to the access probe signal from the base station, the response i) an amount of the indicated main superslot timing offset correction that is an integer multiple of the superslot period, and ii. In the meantime, the base station includes information indicating at least one of a super slot identifier indicating a position of the super slot in the beacon slot in which the access probe signal corresponding to the reception response is received. Operation proceeds from step 1910 to step 1912 where the communication device performs timing adjustments according to the information received in the reception response. Step 1912 includes sub-step 1914. In sub-step 1914, the communication apparatus determines a timing adjustment amount from the information received from the base station and information indicating the time when the access probe signal is transmitted.

  In some embodiments, the received response from the base station includes a superslot identifier indicating the location of the superslot in the beacon slot during which the base station received the access probe signal, and the information included in the response Performing transmission timing adjustments in response to the beacon slot in which the access probe was transmitted indicates the superslot identifier included in the received response and the superslot position relative to the downlink timing reference point Determining a main superslot timing offset from the information, the main superslot timing offset being an integer multiple of the duration of the superslot. In some such embodiments, the received response further includes sub-superslot timing correction information including a sub-superslot time offset, and performing the transmission timing adjustment includes determining the determined main superslot timing offset and sub-superslot Including adjusting the transmission timing by an amount corresponding to the sum of the time offsets.

  In various embodiments, the received response from the base station includes a main superslot timing offset that is an integer multiple of the superslot period and a subsuperslot time offset that is a time offset less than the superslot period. Includes slot timing correction information. In some such embodiments, performing the transmission timing adjustment includes adjusting the transmission timing by an amount corresponding to the sum of the main superslot timing offset and the sub superslot time offset. In some such embodiments, the main superslot timing offset and the subsuperslot time offset are communicated as part of a single encoded value. In other embodiments, the main superslot timing offset and the subsuperslot time offset are communicated as two separate encoded values.

  FIG. 20 illustrates a base station having a downlink timing structure that includes multiple superslots that are repeated in a periodic manner, and operating a wireless communication terminal in a system in which each superslot includes multiple OFDM symbol transmission periods. 2 is a flowchart 2000 of an exemplary method. Operation starts in step 2002 where the wireless terminal is powered and initialized. Operation proceeds from start step 2002 to step 2004, where the wireless terminal responds to whether the base station from which the wireless terminal is requesting to transmit an uplink signal is a satellite base station or a terrestrial base station. Is operated to determine whether or not. Based on the determination of step 2004, operation proceeds from step 2006 to step 2008 if it is a satellite BS, or to step 2010 if the base station is a terrestrial base station.

  In step 2008, the wireless terminal is operated to perform a first uplink timing synchronization process, the first timing uplink synchronization process supporting communication of an uplink timing correction signal to the communication terminal. Step 2008 includes sub-steps 2012, 2014, and 2016. In sub-step 2012, the wireless terminal is operated to send an access probe signal to the satellite base station 2012. In sub-step 2014, the wireless terminal is operated to receive a response to the access probe signal from the base station, the response being i) an amount of the indicated main superslot timing offset correction that is an integer multiple of the superslot period. And ii) at least one of a super slot identifier indicating the position of the super slot in the beacon slot during which the base station received the access probe signal corresponding to the reception response. Next, in step 2016, the wireless terminal performs transmission timing adjustment according to the information included in the reception response.

  In step 2010, the wireless terminal performs a second uplink timing synchronization process, and the second uplink timing synchronization process is different from the first uplink timing synchronization process. Step 2010 includes sub-steps 2018, 2020, and 2022. In sub-step 2018, the wireless terminal transmits an access probe signal to the ground base station. In step 2018, the wireless terminal receives a response to the access probe signal from the terrestrial base station, and the response includes information indicating a time correction that is less than the duration of the superslot. In some embodiments, the timing correction is less than the access interval period. In some embodiments, the timing correction is less than half the access interval period. Then, in step 2022, the wireless terminal performs transmission timing adjustment according to the information contained in the response received from the terrestrial base station, and the timing adjustment reduces the transmitter timing to an amount less than the superslot period. Only involves changing.

  FIG. 21 is a drawing of an exemplary wireless terminal 2100 (eg, mobile node) implemented in accordance with the present invention. The exemplary WT 2100 can be used in various embodiments of the wireless communication system of the present invention. Exemplary WT 2100 includes a receiver 2102, a transmitter 2104, a processor 2106, and a memory 2108 that are coupled together via a bus 2110 on which various elements can exchange data and information. Memory 2108 includes routine 2120 and data / information 2122. The processor 2106 (eg, CPU) executes routines and uses the data information 2122 in the memory 2108 to control the operation of the WT 2100 and implement the method of the present invention.

  A receiver 2102 (eg, an OFDM receiver) includes a beacon signal and a response signal that includes timing adjustment information, via which the WT 2100 is coupled to a receive antenna 2112 that can receive a downlink signal from the base station. Is done. A transmitter 2104 (eg, an OFDM transmitter) is coupled to a transmit antenna 2116 through which the WT 2100 can transmit uplink signals to the base station, including the access probe signal. The timing of the access probe signal includes an offset from the superslot, in which the superslot and which beacon slot send a given access probe signal can be controlled by the transmitter 2104. Receiver 2102 includes a decoder module 2114 that is used to decode downlink signals, while transmitter 2104 includes an encoder module 2118 for encoding uplink signals.

  Routine 2120 includes a communication routine 2124 for implementing a communication protocol used by WT 2100 and a WT control routine 2125 for controlling the operation of WT 2100. The WT control routine 2125 includes a received signal processing module 2126, an encoding module 2128, a transmitter control module 2130, a monitoring module 2132, a timing correction module 2134, a decoder module 2136, and a position-based timing adjustment module 2138. Including. Received signal processing module 2126 processes the signal including the beacon signal to determine a downlink timing reference point from the at least one beacon signal. In some embodiments, an encoding module 2128 that operates alone or in conjunction with the encoder 2118 encodes information in the access probe signal that identifies the superslot index corresponding to the access probe signal. In some embodiments, the WT identifier and / or unique access probe identifier is encoded and included in the access probe signal. Transmitter control module 2130 operates to control operation of transmitter 2104 and controls encoded access probe signals that will be transmitted using timing offsets (eg, different timing offsets for different access probes). Including that. In some embodiments, the transmitter control module 2130 controls the transmission of the continuous access probe to exceed the signal processing time plus twice the signaling time from the WT to the base station, eg, WT 2100 Makes it possible to determine whether an access probe is responding before issuing another access probe. The monitoring module 2132 is used to determine whether a response to the access probe signal has been received from the base station. The timing correction module 2134 corresponds to the monitoring module 2132 and performs transmission timing adjustment according to the information included in the received access probe response. Decoder module 2136, operating alone or in conjunction with decoder 2114, decodes the information in the response that identifies one of the access probe signals. The position-based timing adjustment module 2138 determines the time to transmit the first access probe according to the position information determined from the signal received from the ground base station. The position-based timing adjustment module 2138 can be used to reduce timing ambiguities associated with satellite base stations due to large coverage areas, thereby providing the necessary access associated with the satellite base stations. Reduce the number of probes and / or the average time of the access process.

  Data / information 2122 includes timing / frequency structure information 2140, user / device / session / resource information 2142, and a plurality of access probe signal information sets (first access probe signal information 2144, ..., Nth access. Probe information 2146), received beacon signal information 2148, timing reference point information 2150, initial timing offset information 2152, step size information 2154, received response signal information 2156, timing adjustment information 2158, terrestrial BS / satellite BS location information 2160. Timing / frequency structure information 2140 includes downlink and uplink timing and frequency structure information, periodicity information, indexing information, OFDM symbol transmission time interval information, and OFDM symbols such as slots, superslots, and beacon slots. Information regarding grouping of transmission time intervals, base station identification information, beacon signal information, repetition interval information, access interval information, uplink carrier frequency, downlink carrier frequency, uplink tone block information, It includes downlink tone block information, uplink and downlink tone hopping information, base station identification information, and the like. Timing / frequency structure information 2140 includes information corresponding to a plurality of base stations that may be present in the wireless communication system. The user / device / session / resource information 2142 includes information corresponding to a user of the WT 2100 and, for example, an identifier, an address, routine information, an assigned air link resource (eg, a downlink traffic channel segment, a multi-channel associated with a terrestrial base station). Peers in a communication session with WT 2100, including uplink traffic channel segment for tone mode, single dedicated logical tone for uplink signaling with satellite BS, base station assigned WT user information, etc. ). The first access probe information 2144 includes, for example, timing offset information corresponding to the access probe, information identifying the super slot index, encoding information, information identifying the beacon slot, etc. in relation to the start of the super slot. . The Nth access probe information 2146 includes, for example, timing offset information corresponding to the access probe, information identifying the superslot index, encoding information, information identifying the beacon slot, etc. in relation to the start of the superslot. . Different sets of access probe information (2144, 2146) may partially or completely include different information (eg, different timing offsets, different superslot index values or different timing offsets, the same superslot value). Access probe signal information (2144, 2146) may include user identification information (eg, WT user identifier and / or unique access probe signal identifier) and tone information associated with the access probe signal. Received beacon signal information 2148 is information from the received beacon signal (eg, information related to the beacon associated with a particular base station), carrier frequency and / or sector, beacon signal strength information, WT establishes a timing reference point. Information that makes it possible. Timing reference point information 2150 includes information that establishes a reference point, eg, determined using downlink beacon signaling (eg, beacon slot start upon which superslot indexing is based). Access probe signaling transmission timing can be referenced with respect to established timing reference point information 2150. The initial timing offset information 2152 includes information identifying the initial timing offset value used in the timing offset calculation for the access probe, for example, for the superslot start. The step size information 2154 is an initial timing offset in integer multiples to determine the offset from the start of the superslot for a particular access probe, eg, with different access probes using different integer multiples of the step size timing offset. Includes information identifying a fixed step size timing offset to be added. The fixed step size is, in some embodiments, less than the base station access interval period, during which the base station corresponds to the access probe signal. Reception response signal information 2156 includes information received in response to access probe signaling, including timing correction information. Timing correction information may be encoded. In some embodiments, the response signal information 2156 also includes information identifying which one of the access probe signals is being responded, eg, via a WT identifier and / or a unique access probe signal identifier. . Timing adjustment information 2158 includes timing correction information extracted from the reception response signal and information indicating a change to transmission timing as a result of applying the correction information. Ground base station / satellite base station position information 2160 includes information indicating the position of the ground base station and the position of the satellite base station in the system. Information 2160 may include information that correlates cell coverage areas or satellite base stations with terrestrial base stations.

  FIG. 23 is a drawing of an exemplary wireless terminal 2300 (eg, mobile node) implemented in accordance with the present invention. The exemplary WT 2100 can be used in various embodiments of the wireless communication system of the present invention. Exemplary WT 2300 includes a receiver 2302, a transmitter 2304, a processor 2306, and a memory 2308 that are coupled together via a bus 2310 over which various elements can exchange data and information. Memory 2308 includes routines 2320 and data / information 2322. The processor 2306 (eg, CPU) executes routines and uses the data information 2322 in the memory 2308 to control the operation of the WT 2300 and perform the method of the present invention.

  A receiver 2302 (eg, an OFDM receiver) is coupled to a receive antenna 2312 through which a WT 2300 can receive a downlink signal from a base station, including a beacon signal and a response signal that includes timing adjustment information. The A transmitter 2304 (eg, an OFDM transmitter) is coupled to a transmit antenna 2316 through which the WT 2300 can transmit uplink signals to the base station, including access probe signals. The timing of the access probe signal includes an offset from the superslot, in which which superslot and which beacon slot send a given access probe signal can be controlled by the transmitter 2304. . Receiver 2302 includes a decoder module 2314 that is used to decode downlink signals, while transmitter 2304 includes an encoder module 2318 for encoding uplink signals.

  Routine 2320 includes a communication routine 2324 for implementing the communication protocol used by WT 2300 and a WT control routine 2325 for controlling the operation of WT 2300. The WT control routine 2325 includes a received signal processing module 2326, an encoding module 2328, a transmitter control module 2330, a monitoring module 2332, a timing adjustment module 2334, and a decoder module 2136. Received signal processing module 2326 processes signals including beacon signals to determine a downlink timing reference point from at least one beacon signal. In some embodiments, an encoding module 2328 that operates alone or with the encoder 2318 encodes information in the access probe signal that identifies the corresponding access probe signal, for example, within a sequence of access probe signals. To do. The wireless terminal identifier and / or unique access probe signal identifier may be encoded to allow discrimination between multiple WTs in a system that can transmit access probes. Transmission control module 2330 operates to control the operation of transmitter 2304 and controls encoded access probe signals that will be transmitted using timing offsets (eg, different timing offsets for different access probes). including. In some embodiments, the time between consecutive access probes may be less than a larger superslot period and twice the time required for the signal to travel from the WT to the base station. For example, consider that a superslot includes one access interval. However, the timing ambiguity exceeds the access interval but may be less than the superslot period, and the WT may identify, for example, access probes to cover possible timing range ambiguities within the superslot. Can be transmitted with a time interval less than the access interval. The monitoring module 2332 is used to determine whether a response to the access probe signal has been received from the base station. In response to the monitoring module 2332, the timing adjustment module 2334 performs transmission timing adjustment according to information included in the received access probe response. A decoder module 2336, operating alone or in conjunction with decoder 2314, decodes the information in the response that identifies one of the access probe signals.

  Data / information 2322 includes timing / frequency structure information 2340, user / device / session / resource information 2342, and a plurality of access probe signal information sets (first access probe signal information 2344, ..., Nth access. Probe information 2346), received beacon signal information 2348, timing reference point information 2350, access probe spacing / offset information 2352, received response signal information 2356, and timing adjustment information 2358. Timing / frequency structure information 2340 includes downlink and uplink frequency structure information, periodicity information, indexing information, OFDM symbol transmission time interval information, and OFDM symbol transmission times such as slots, superslots, and beacon slots. Information on interval grouping, base station identification information, beacon signal information, repetition interval information, access interval information, uplink carrier frequency, downlink carrier frequency, uplink tone block information, and downlink It includes tone block information, uplink and downlink tone hopping information, base station identification information, and the like. Timing / frequency structure information 2340 includes information corresponding to multiple base stations that may be present in the wireless communication system. User / device / session / resource information 2342 includes information corresponding to the user of WT 2300 and, for example, identifiers, addresses, routine information, assigned air link resources (eg, downlink traffic channel segments, Supports peers in a communication session with WT 2300, including uplink traffic channel segment for tone mode, single dedicated logical tone for uplink signaling with satellite BS, base station assigned WT user information, etc. Information. The first access probe information 2344 includes, for example, timing offset information corresponding to the access probe, information identifying the super slot index, encoding information, information identifying the beacon slot, etc. in relation to the start of the super slot. . The Nth access probe information 2346 includes, for example, timing offset information corresponding to the access probe, information identifying the superslot index, encoding information, information identifying the beacon slot, etc. in relation to the start of the superslot. . Different sets of access probe information (2344, 2346) may partially or completely contain different information (eg, different timing offsets but the same superslot). The access probe signal information (2344, 2346) may include user identification information (eg, WT user identifier and / or unique access probe signal identifier) and tone information associated with the access probe signal. Received beacon signal information 2348 includes information from the received beacon signal (eg, information related to the beacon associated with a particular base station), carrier frequency and / or sector, beacon signal strength information, WT establishes timing reference point. Information that makes it possible. Timing reference point information 2350 includes information that establishes a reference point, eg, determined using downlink beacon signaling (eg, beacon slot start upon which superslot indexing is based). Access probe signaling transmission timing can be referenced with respect to established timing reference point information 2350. Access probe spacing / offset information 2352 includes timing information regarding access probes in the sequence of access probes (eg, delta time intervals between consecutive access probes). For example, if each access interval period is less than a superslot, but the timing ambiguity exceeds the access interval period, several consecutive access probes may be spaced by a delta time interval that is less than or equal to the access interval period, and Numbers are like covering timing ambiguities. Reception response signal information 2356 includes information received in response to access probe signaling, including timing correction information. The timing correction information may be encoded. In some embodiments, the response signal information 2356 also includes information identifying which one of the access probe signals in the sequence of continuous access probes is being responded to. The timing adjustment information 2358 includes timing correction information extracted from the reception response signal and information indicating a change to the transmission timing as a result of application. Receive response signal information 2356 may include a WT identifier and / or a unique access probe signal identifier.

  FIG. 24 is a drawing of an exemplary wireless terminal 2400 (eg, mobile node) implemented in accordance with the present invention. The exemplary WT 2400 can be used in various embodiments of the wireless communication system of the present invention. Exemplary WT 2400 includes a receiver 2402, a transmitter 2404, a processor 2406, and a memory 2408 that are coupled together via a bus 2410 on which various elements can exchange data and information. Memory 2408 includes routines 2420 and data / information 2422. The processor 2406 (eg, CPU) executes routines and uses the data information 2422 in the memory 2408 to control the operation of the WT 2400 and implement the method of the present invention.

  A receiver 2402 (eg, an OFDM receiver) couples to a receive antenna 2412 through which a WT 2400 can receive a downlink signal from a base station, including a beacon signal and a response signal that includes timing adjustment information. Is done. A transmitter 2404 (eg, an OFDM transmitter) is coupled to a transmit antenna 2416 through which the WT 2400 can transmit uplink signals to the base station, including access probe signals. The timing of the access probe signal includes an offset from the superslot, in which which superslot and which beacon slot send a given access probe signal therein can be controlled by the transmitter 2404. It is. Receiver 2402 includes a decoder module 2414 that is used to decode the downlink signal, while transmitter 2404 includes an encoder module 2418 for encoding the uplink signal.

  Routines 2420 include a communication routine 2424 for implementing the communication protocol used by WT 2400 and a WT control routine 2425 for controlling the operation of WT 2400. The WT control routine 2425 includes a received signal processing module 2426, an encoding module 2428, a transmitter control module 2430, a monitoring module 2432, a transmission timing correction module 2434, and a receiver control and decoding module 2436. Receive signal processing module 2426 processes signals including beacon signals to determine a downlink timing reference point from at least one beacon signal. Encoding module 2128, operating alone or with encoder 2118, encodes information in the uplink signal (eg, a WT identifier and / or a unique access probe in an access probe signal to be transmitted by WT 2400). Encoding the identifier) allows the access probe to be distinguished by the BS from other access probes that may have been transmitted by other WTs. Transmitter control module 2430 operates to control the operation of transmitter 2404 and is an access probe that will be transmitted using a timing offset (eg, a timing offset that is different from the start of the superslot for different access probes). Including controlling the signal. In some embodiments, the transmitter controller module 2430 controls the transmission of the continuous access probe to exceed the signal processing time plus twice the signaling time from the WT to the base station, for example, Allows the WT 2400 to determine whether an access probe is responding before issuing another access probe. The monitoring module 2432 is used to determine whether a response to the access probe signal has been received from the base station. The transmission timing adjustment module 2434 corresponds to the monitoring module 2432 and performs transmission timing adjustment according to information included in the reception access probe response signal. For example, the transmission timing adjustment module 2434 may include information in the received response signal (eg, sub-superslot timing offset correction information) along with information known to the WT 2400 about when the access probe was transmitted to calculate the timing adjustment. 2464), and one of the main superslot timing offset correction values, or a superslot position indicator indicating base station reception. In some embodiments, the received response signal conveys sub-superslot timing offset information, eg, via encoded bits in the response signal, and the main superslot timing offset information passes through the transmission time of the response signal. Reportedly. In some embodiments, the receiver control and decoder module 2436 operating alone or with the encoder 2414 receives the access probe response signal from the base station and i) is an integer multiple of the superslot period. At least one of the amount of main superslot timing offset correction performed and ii) the superslot identifier indicating the position of the superslot in the beacon slot during which the base station received the access probe signal corresponding to the reception response Extract the information in the response. In some embodiments, the main superslot timing offset is encoded with the subsuperslot time offset as a single encoded value, and module 2436 performs a decoding operation. In some embodiments, the main superslot timing offset is encoded separately from the subsuperslot time offset as two separately encoded values, and module 2436 performs a decoding operation. In some embodiments, the subslot timing offset is conveyed via the encoded bits of the response signal, and the main superslot offset is, for example, in the response signal within the response signal that is offset by a different amount, It is conveyed by controlling the transmission time of the response signal. In some embodiments, the response signal is a WT identifier and / or a unique access probe signal identifier so that the WT 2400 can recognize that the response signal is directed to the WT 2400 rather than another WT in the system. 2465 is also included.

  Data / information 2422 includes timing / frequency structure information 2440, user / device / session / resource information 2442, and a plurality of access probe signal information sets (first access probe signal information 2444, ..., Nth access. Probe information 2446), reception beacon signal information 2448, timing reference point information 2450, initial timing offset information 2452, step size information 2454, reception response signal information 2456, and timing adjustment information 2458. Timing / frequency structure information 2440 includes downlink and uplink timing and frequency structure information, periodicity information, indexing information, OFDM symbol transmission time interval information, and OFDM symbols such as slots, superslots, and beacon slots. Information regarding grouping of transmission time intervals, base station identification information, beacon signal information, repetition interval information, access interval information, uplink carrier frequency, downlink carrier frequency, uplink tone block information, It includes downlink tone block information, uplink and downlink tone hopping information, base station identification information, and the like. Timing / frequency structure information 2440 includes information corresponding to multiple base stations that may be present in the wireless communication system. User / device / session / resource information 2442 includes information corresponding to the user of WT 2400 and, for example, identifiers, addresses, routine information, assigned air link resources (eg, downlink traffic channel segments, Supports peers in a communication session with WT 2400, including uplink traffic channel segment for tone mode, single dedicated logical tone for uplink signaling with satellite BS, base station assigned WT user information, etc. Information. The first access probe information 2444 includes, for example, timing offset information corresponding to the access probe, information identifying the super slot index, information identifying the beacon slot, and the like in relation to the start of the super slot. The Nth access probe information 2446 includes, for example, timing offset information corresponding to the access probe, information identifying the superslot index, information identifying the beacon slot, and the like in relation to the start of the superslot. Different sets of access probe information (2444, 2446) may partially or completely include different information (eg, different timing offsets, different superslot index values or different timing offsets, the same superslot value). The access probe signal information (2444, 2446) may include user identification information (eg, a WT identifier and / or a unique access probe signal identifier) and tone information associated with the access probe signal. The WT identifier and / or unique access probe signal identifier may be encoded into the access probe signal so that the BS can distinguish among multiple access probes (eg, from different WTs in the system) May include an identifier in the response signal, allowing the WT 2400 to know that the response signal is for the WT 2400. Received beacon signal information 2448 includes information from the received beacon signal (eg, information about the beacon associated with a particular base station), carrier frequency and / or sector, beacon signal strength information, WT establishing timing reference point. Includes information to enable. Timing reference point information 2450 includes information that establishes a reference point, eg, determined using downlink beacon signaling (eg, beacon slot start based on which superslot indexing is based). Access probe signaling transmission timing can be referenced with respect to established timing reference point information 2450. The initial timing offset information 2452 includes information identifying the initial timing offset value used in the timing offset calculation with respect to the access probe, eg, in connection with superslot start. The step size information 2454 is an initial timing offset in integer multiples to determine the offset from the start of the superslot for a particular access probe, eg, with different access probes using different integer multiples of the step size timing offset. Includes information identifying a fixed step size timing offset to be added. The fixed step size is, in some embodiments, less than the base station access interval period, during which the base station corresponds to the access probe signal. Reception response signal information 2456 includes information received in response to access probe signaling, including timing correction information. Receive response signal information 2456 includes a WT identifier and / or a unique access probe signal identifier 2465 that allows WT 2400 to recognize a response signal directed to itself rather than another WT in the system. It's okay. In some embodiments, the response signal information 2156 may be an access probe transmitted by the WT 2400, eg, if the WT 2400 transmits multiple access probes within a time interval that is less than twice the signal transmission time from the WT to the BS. It also includes information identifying which one of the signals is being answered. Timing correction information may be encoded. In some embodiments, the response signal information 2156 also includes information identifying which one of the access probe signals is being responded to. Receive response signal information 2456 includes sub-superslot timing offset correction information 2460 and, in some embodiments, main superslot timing offset correction information 2460 (eg, an integer multiple of the superslot period) and, for example, a base station therebetween Includes at least one of the superslot location identifiers 2462 that identify the location of the superslot in the beacon slot that received the access probe signal corresponding to the received response. The timing adjustment information 2458 indicates, for example, timing correction information extracted from the reception response signal in combination with known timing information corresponding to the access probe, and a change in transmission timing as a result of applying the correction information. Information.

  FIG. 22 illustrates a method of operation of a base station (eg, satellite base station), according to an illustrative embodiment of the invention. All or part of the method may be used depending on the particular embodiment and the type of wireless terminal signaling transmitted to the base station (eg, the type of information encoded regarding the transmit access probe) It is.

The method begins at step 2202, for example, when the base station is initialized and put into operation. The operation proceeds along parallel paths to steps 2203 and 2204 that may be performed in parallel. In step 2203, the base station transmits a beacon signal on a periodic basis according to a predetermined downlink timing structure, and at least one beacon signal is transmitted during each beacon slot. In various embodiments, a beacon signal is a signal that is transmitted at a higher power level than is typically used to transmit user data (eg, text, video, or application data). In some embodiments, the beacon signal is a narrowband signal. In some embodiments, the beacon signal is implemented as a single tone signal that is transmitted for one small number of continuous signal transmission periods (eg, less than a period of 3 or 4 consecutive OFDM symbols). The beacon signal is transmitted on a periodic basis determined by the downlink timing structure.

  In step 2204, which may occur in parallel with the beacon transmission step 2203, the base station monitors to detect access probe signals, for example during access intervals that occur on a periodic basis. In some embodiments, the periodic access interval has a duration that is less than the duration of the downlink superslot. The access probe signal may be received from one or more communication devices that have not yet fully achieved uplink timing synchronization with the base station. Superslot and / or sub-superslot uplink timing correction may be required before the wireless terminal transmitting the access probe will achieve symbol level uplink timing synchronization with the base station. For each access probe signal detected in step 2204, operation proceeds to step 2206. In step 2206, the base station determines an indication of a downlink superslot period at the base station during which an access probe signal was received. This may be different from the superslot in which the transmitting communication device thought it was transmitting the access probe. The determination of which downlink superslot access probe signal was received can be made using internal base station timing information and an awareness of when an access probe was received.

  Operation proceeds from step 2206 to 2208. In step 2208, the base station may transmit information that may be encoded with respect to the signal (eg, an access probe identifier, a communication device identifier that identifies the transmitting communication device, and / or, for example, access by the transmitting device therein). A decoding operation is performed on the access probe signal to detect a downlink superslot identifier (indicating the superslot in the beacon slot that transmitted the probe).

  Access probe information is decoded and operation proceeds to steps 2210 and 2212. In step 2210, the base station is to be performed by the communication device that transmitted the receive probe to achieve proper symbol level timing within the superslot with respect to the signal transmitted to the base station (eg, OFDM signal). The sub-superslot uplink transmission timing correction offset is determined. This timing correction value is a value indicating correction that is less than the superslot period. Operation proceeds from step 2210 to step 2214.

  Step 2212 is an optional step performed in some embodiments where a superslot indicator is encoded for a received access probe. Performed in some embodiments, but not necessarily in all embodiments, at step 2212 as indicated by the downlink superslot in which the access probe was received and the decoded superslot identifier In addition, the main superslot timing offset correction is determined from the difference between the indices of the superslots in which the access probes are transmitted. Operation proceeds from step 2212 to step 2214.

  Step 2214 is a step in which a response to the received access probe is generated and transmitted. In some embodiments, the response is transmitted in a downlink superslot having a predetermined downlink superslot offset from the downlink superslot period in which the access probe to which the response corresponds is received by the base station. Is done. The superslot offset is sufficient for the base station to process and generate the required response (eg, one or two superslots from the superslot in which the access probe was received). Such an embodiment in which a response is transmitted in a downlink superslot with a predetermined known superslot offset from the superslot in which the response was received is such that the wireless terminal may receive a superslot timing offset error from the response timing. Makes it possible to estimate.

  In some embodiments in which the access probe signal transmits a response at a predetermined superslot offset relative to when the access probe is received, the wireless terminal receiving the access probe response is implemented according to the following equation: Calculate the main timing adjustment that will be.

  Main timing adjustment = 2 × (indicator of superslot in which response to access probe is received−superslot indicator determined by communication apparatus in which access probe is transmitted) −fixed superslot delay) × Super slot period. The fixed super slot delay depends on a predetermined offset. The double factor takes into account that the delay involved is a round trip delay, while the multiplication by the period of the downlink superslot takes into account the period of the superslot.

  At step 2214, the sub-superslot uplink timing offset correction determined at step 2210 is encoded in the response. In addition, other information may also be encoded into the generated access probe response signal. Each of the elements may be individually encoded, for example, as individual error values, or may be combined with, for example, main superslot error information and subsuperslot error information encoded as a single value, for example. . In sub-step 2224, the main superslot uplink timing offset correction (eg, the correction value generated in step 2212) is encoded in the response signal. In sub-step 226, a superslot identifier indicating the indication of the downlink superslot in which the access probe signal was received is encoded in the response signal. In sub-step 2228, the communication device identifier and / or the access probe identifier corresponding to the received access probe being responded to is encoded in the response signal. Identification of communication devices to which responses are directed is particularly useful in multi-user systems where multiple devices can make requests, for example, as part of a competition-based access process. Operation proceeds from step 2214 to step 2230, where the generated probe is transmitted as an access probe response signal. The process corresponding to the received detected access probe ends at step 2232, but reception and processing of other access probes can continue.

  FIG. 25 is a diagram of an exemplary base station 2500 (eg, satellite-based base station) implemented in accordance with the present invention and using the methods of the present invention. Exemplary base station 2500 may be a BS of an exemplary wireless communication system implemented in accordance with the present invention. Since the base station provides network connectivity to the WT, the base station 2500 may be referred to as an access node. Base station 2500 includes a receiver 2502, a transmitter 2504, a processor 2506, and a memory 2508 that are coupled together via a bus 2510 over which various elements can exchange data and information. Receiver 2502 includes a decoder 2512 for decoding uplink signals received from the WT, including, for example, access probe signals. Transmitter 2504 includes an encoder 2514 for encoding downlink signals to be transmitted to the WT, including, for example, downlink beacon signals and downlink response signals for access probes. Receiver 2502 and transmitter 2504 are each coupled to antennas (2516, 2518) through which uplink signals are received from the WT and downlink signals are transmitted to the WT, respectively. In some embodiments, the same antenna is used for receiver 2502 and transmitter 2504. In addition to communicating with the WT, the base station 2500 can communicate with other network nodes. In some embodiments where BS 2500 is a satellite base station, the BS communicates with the ground station using directional antennas and high-capacity links, and the ground station communicates with other network nodes (eg, other base stations, routers). , AAA server, home agent node and the Internet). In some such embodiments, for the BS-network node base station link, the same receiver 2502, transmitter 2504 and / or antenna as previously described with the BS-WT communication link is used, while In other embodiments, separate elements are used for different functions. In embodiments where BS 2500 is a terrestrial base station, BS 2500 includes a network interface that couples BS 2500 to other network nodes and / or the Internet. Memory 2508 includes routines 2520 and data / information 2522. A processor 2506 (eg, CPU) executes routine 2520 and uses data / information 2522 in memory 2508 to control the operation of base station 2500 and perform the method of the present invention.

  Memory 2508 includes a communication routine 2524 and a base station control routine 2526. Communication routine 2524 implements various communication protocols used by base station 2500. Base station control routine 2526 includes a scheduler module 2528 that allocates segments (eg, downlink traffic channel segments) to a WT, a transmitter control module 2530, a receiver control module 2536, an encoder module 2546, and access probe decoding. And a processing module 2548 and a timing correction determination module 2550.

The transmitter control module controls the operation of the transmitter 2504. Transmitter control module 2530 includes a beacon module 2532 and an access probe response module 2534. The beacon module controls transmission of beacon signals (eg, transmission of at least one beacon signal) between beacon slots. In some embodiments, the beacon signal is a single tone signal. In some embodiments, the beacon signal has a period that is less than three OFDM symbol transmission periods. Access probe response module 2542 controls the generation and transmission of response signals in response to access probe signals.

  Receiver control module 2536 includes an access probe reception and detection module 2540. The receiver control module 2536 controls the operation of the receiver 2502. Access probe reception and detection module 2540 is used to receive and detect access probe signals from wireless terminals. The access probe detection module 2540 includes an access probe detection module 2542 and an access time interval determination module 2544. The access time interval determination module 2544 identifies a predetermined periodic period that occurs between the portions of each superslot during a beacon slot, said portion being less than half of the superslot, Sometimes referred to as an access interval or slot reserved for receiving an access probe. Access probes that arrive outside the access interval are treated as interference by the base station and are not responded. In some embodiments, the access interval is less than 25% of the superslot interval. For example, the access interval may be 8 or 9 OFDM symbol transmission intervals corresponding to a superslot of 114 OFDM symbol transmission intervals. In some embodiments, the OFDM symbol transmission interval is approximately 100 microseconds. Access probe detection module 2542 detects and processes incoming access probes that arrive during a time interval that is deemed acceptable by access interval determination module 2544.

  In some embodiments, the encoding module 2546, operating alone or in conjunction with the encoder 2514, is a superslot that indicates in the response signal the location of the superslot in the beacon slot during which the base station received the access probe signal. Contains an identifier. In some embodiments, an encoding module that operates alone or in conjunction with encoder 2514 encodes sub-superslot timing correction information in a response signal, wherein the superslot timing correction information has a timing that is less than the duration of the superslot. Indicates adjustment.

  The access probe decoding and processing module 2548, operating alone or in conjunction with the decoder 2512, provides encoded information (eg, encoded superslot identifier, encoded information identifying a WT, encoded information identifying an access probe signal). Decode the received access probe signal to recover.

  In some embodiments, the timing correction determination module 2550 determines the main superslot from the difference between the decoded superslot identifier and the superslot index in the beacon slot of the superslot in which the access probe was received. Determine timing offset correction (eg, integer multiple of superslot period). In some embodiments, the timing correction determination 2550 determines the main superslot timing offset correction based on the beacon transmission reference point and the reference point of the received access probe signal. In some such embodiments, the access probe signal carries information identifying the superslot indication during which the WT transmitted the access probe signal. In some such embodiments, the response signal carries timing adjustment information combined by the WT with access signal offset information known to the WT but not known to the BS. In some such embodiments, the sub-superslot timing correction is conveyed in the response signal via encoded bits, while the main timing offset information is conveyed by the response signal transmission time.

  The data / information 2522 includes a plurality of information sets (user 1 / MN session A session B data / information 2554, user N / MN session X data / data) corresponding to the wireless terminal using the base station 2500 as the network connection mechanism point. User data / information 2552 including information 2556). Such WT information includes, for example, WT identifiers, routing information, assigned uplink symbol logical tones, downlink segment assignment information, and user data / information (eg, voice information, text data packets, video, music, etc.). And an encoded block of information. Data / information 2522 also includes system information 2574 including downlink / uplink timing and frequency structure information 2576, beacon signal information 2558, received access probe signal information 2560, and response signal information 2562. The response signal information includes sub super slot timing offset correction information 2572 and at least one of main super slot timing offset correction information 2564, super slot identifier information 2566, communication device identifier information 2568, and access probe identifier information 2570. .

  In some embodiments, the main superslot timing offset correction is an integer multiple of the superslot period. The superslot identifier may be used to indicate the location of the superslot within the beacon slot during which the base station received the access probe signal corresponding to the received response. The communication device identifier may be used to identify the communication device that transmitted the access probe signal corresponding to the reception response. The access probe identifier can be used to identify the access probe to which the response signal corresponds.

  Downlink / uplink timing and frequency structure information 2576 includes OFDM symbol transmission timing information, information corresponding to grouping of OFDM symbols (for example, information on slots, superslots, beacon slots, access intervals, etc.), and beacon timing. And tone information, indexing information (e.g. of superslots in beacon slots), carrier frequencies used for uplink and downlink, and tone blocks used for uplink and downlink , Including tone hopping information used for uplink and downlink, timing relationships and offsets between uplink and downlink timing structures at the base station, periodic periods within the timing structures, and so on.

  The techniques of the present invention may be implemented using software, hardware and / or a combination of software and hardware. The present invention relates to an apparatus, for example, a mobile node such as a mobile terminal implementing the present invention, a base station, and a communication system. The invention also relates to a method, for example a method of controlling and / or operating a mobile node, a base station and / or a communication system (eg a host) according to the invention. The present invention also relates to machine readable media (eg, ROM, RAM, CD, hard disk, etc.) containing machine readable instructions for controlling the machine for the purpose of performing one or more steps according to the present invention.

  In various embodiments, a node described herein can perform one step (eg, signal processing step, message generation and / or transmission step) corresponding to one or more methods of the present invention. Implemented using one or more modules. Thus, in some embodiments, the various functions of the present invention are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the methods or method steps described above involve, for example, a machine (eg, a general purpose computer with or without additional hardware) for the purpose of performing all or part of the methods described above at one or more nodes. To control, it may be implemented using machine-executable instructions such as software contained within a machine-readable medium such as a memory device (eg, RAM, floppy disk, etc.). Accordingly, among other things, the present invention includes a machine-readable medium comprising machine-executable instructions for causing a machine (eg, a processor and associated hardware) to perform one or more steps of the above-described method (s). About.

  The timing synchronization method and apparatus of the present invention can be used by various apparatuses and systems. The method and apparatus of the present invention is described in US patent application Ser. No. 11 / 184,051, filed on the same date as this application and entitled “COMMUNICATIONS SYSTEM, METHODS AND APPARATUS”, which designates the same inventor as this application. It is very suitable for use in combination with the described method and apparatus and may be used in combination with the method and apparatus. This general patent application is expressly incorporated into the present invention by reference and should be considered part of the disclosure of this patent application.

  Although described in the context of an OFDM system, at least some of the methods and apparatus of the present invention are applicable to a wide range of communication systems, including many non-OFDM and / or non-cellular systems.

  Numerous additional variations on the method and apparatus of the present invention described above will be apparent to those skilled in the art from the above description of the invention. Such variations are to be considered within the scope of the invention. In some embodiments, a base station server such as an access node that establishes a communication link with a mobile node (WT) using OFDM signals. In various embodiments, the WT includes a cell phone, notebook computer, personal data assistant (PDA), or receiver / transmitter circuitry and logic and / or routines to implement the method of the present invention. Implemented as other portable devices.

1 is a diagram of an exemplary wireless communication system implemented in accordance with the present invention and using the methods of the present invention. FIG. 2 is a diagram of an exemplary base station (eg, a ground-based base station) implemented in accordance with the present invention and using the method of the present invention. FIG. 2 is a diagram of an exemplary base station (eg, satellite based base station) implemented in accordance with the present invention and using the method of the present invention. FIG. 2 is a diagram of an exemplary wireless terminal (eg, mobile node) implemented in accordance with the present invention and using the method of the present invention. FIG. 6 illustrates exemplary uplink information bit encoding for an exemplary WT (eg, MN) operating in a single tone uplink mode of operation in accordance with various embodiments of the invention. FIG. 3 illustrates an exemplary OFDM wireless multiple-access communication system including a hybrid of base stations that are both ground-based and space-based, in accordance with various embodiments of the present invention. FIG. 6 illustrates exemplary backhaul interconnectivity between the various satellite-based and ground-based base stations of FIG. 6 is a flowchart of an exemplary method of operating a wireless terminal (eg, mobile node) in accordance with the present invention. As a result, the example satellite base station and the differently located at different points within the cellular coverage area of the satellite base station on the surface of the earth, resulting in timing synchronization considerations addressed in accordance with the method and apparatus of the present invention. FIG. 3 illustrates a relatively long round trip signaling time between mobile nodes and very different signal path lengths. FIG. 2 illustrates an exemplary hybrid system that includes both terrestrial and satellite base stations and a wireless terminal that utilizes terrestrial base station location information to reduce round drip timing ambiguity with respect to satellite base stations. . Illustrates an embodiment in which multiple terrestrial base stations are associated with the same satellite base station coverage area, and terrestrial base station location and / or connection information is used to reduce WT / satellite base station timing ambiguity FIG. In an exemplary satellite / terrestrial hybrid wireless communication system, a round trip signal delay between a satellite base station and a ground-located wireless terminal is a typical superslot time used in some ground-based wireless communication systems. It is a figure which illustrates having exceeded an interval. FIG. 6 is a diagram illustrating a function of encoding an access probe signal with information identifying a relative time interval value (eg, superslot index value) within a larger relative time interval (eg, beacon slot) within a timing structure range. FIG. 6 is a diagram in which the encoded information is used in an access process to determine timing synchronization between a satellite base station and a WT according to the present invention. FIG. 6 illustrates the ability to use multiple access probe signals with different timing offsets so that timing synchronization between the satellite base station and the WT can be further resolved within a smaller time interval in accordance with the present invention. FIG. 6 further illustrates the concept of a wireless terminal transmitting a plurality of access probes to a satellite base station with different timing offsets in accordance with the present invention. FIG. 3 illustrates exemplary access signaling according to the method of the present invention. FIG. 3 illustrates exemplary access signaling according to the method of the present invention. 2 shows exemplary access signaling according to the method of the present invention. Includes the combination of FIGS. 16 and 16B. 5 is a flowchart of an exemplary method of operation of a wireless terminal for connecting to a base station and performing a timing synchronization operation in accordance with the present invention. 5 is a flowchart of an exemplary method of operation of a wireless terminal for connecting to a base station and performing a timing synchronization operation in accordance with the present invention. Includes the combination of FIGS. 17A and 17B. 2 is a flow diagram of an exemplary method of operating a communication device for use in a communication system. 2 is a flow diagram of an exemplary method of operating a communication device for use in a communication system. 4 is a flow diagram of an exemplary method of operation of an exemplary communication device in accordance with the present invention. 4 is a flow diagram of an exemplary method of operation of an exemplary communication device in accordance with the present invention. 5 is a flowchart of an exemplary method of operating a wireless communication terminal according to the present invention. FIG. 2 is a diagram of an exemplary wireless terminal (eg, mobile node) implemented in accordance with the present invention. 3 is a flowchart of an exemplary method of operating a base station according to the present invention. FIG. 2 is a diagram of an exemplary wireless terminal (eg, mobile node) implemented in accordance with the present invention. FIG. 2 is a diagram of an exemplary wireless terminal (eg, mobile node) implemented in accordance with the present invention. FIG. 2 is an exemplary base station implemented in accordance with the present invention and using the method of the present invention.

Claims (26)

A method of operating a base station having a periodic downlink timing structure where beacon time slots occur on a periodic basis in the downlink, wherein each beacon time slot includes a plurality of superslots representing continuous OFDM symbol transmission time intervals. , The superslots in the beacon slot are identifiable by using a superslot indicator, each superslot includes a plurality of symbol transmission periods, and the method comprises:
Monitoring to detect reception of an access probe signal;
Sending a reply to the access probe signal, wherein the reply is i) an integer multiple of the superslot period, the indicated main superslot timing offset correction amount, ii) the access probe signal corresponding to the reply Iii) identifier identifying the communication device that transmitted the access probe signal corresponding to the reply, iv) the reply and a includes information indicating at least one of an identifier that identifies the access probe corresponding to,
The monitoring is a method of recognizing only an access probe signal received within an access interval window, and accepting an access probe signal outside the access interval window as interference noise .   Monitoring to detect reception of the access probe signal is performed on a predetermined periodic basis according to the occurrence of access intervals in the uplink timing structure, each access interval being less than the downlink superslot period. The method according to claim 1, which is short.   The method of claim 1, wherein sending a reply to the access probe signal comprises sending the reply in a downlink superslot having a predetermined superslot time offset from the received time.   4. The method of claim 3, wherein transmitting the reply includes transmitting a device identifier that identifies the device that transmitted the transmitted access probe signal and the sub-superslot timing correction indicator value.   The method of claim 2, wherein the monitoring is performed for a portion of each access interval that occurs in an uplink timing structure.   The method of claim 1, further comprising transmitting at least one beacon signal during each beacon slot.   The method of claim 6, wherein the beacon signal is a single tone signal.   The method of claim 7, wherein the beacon signal has a duration that is less than three OFDM transmission periods.   The method of claim 6, wherein the access probe signal is an OFDM signal.   Transmitting a response to the received access probe signal encodes a downlink superslot identifier indicating a location of the superslot in a downlink beacon slot that is a period in which the base station receives the access probe signal The method of claim 9 comprising: Sending a reply to the received access probe signal further
Includes encoding the sub superslot uplink timing correction information in the reply,
The method of claim 10, wherein the sub- superslot uplink timing correction information indicates a timing adjustment value that is shorter than a superslot duration. The received access probe signal includes an encoded downlink superslot identifier, and the method further includes:
Decoding the encoded downlink superslot identifier;
From the difference between the superslot index in the downlink beacon slot of the downlink superslot, which is the period during which the access probe signal is received, and the decoded downlink superslot identifier, the integer of the duration of the downlink superslot Determining a main superslot timing offset correction amount that is doubled ,
The method of claim 10 , wherein the periodic downlink timing structure is known by transmitting a downlink signal including a downlink beacon signal for each beacon slot . The main super slot timing offset correction amount is an integer value.
Furthermore sending a reply to the received access probe signal The method of claim 9 comprising encoding the main superslot timing correction amount the determined in the reply. Sending a reply to the received access probe signal further comprises encoding sub-superslot uplink timing correction information in the reply;
The method of claim 13, wherein the superslot uplink timing correction information indicates a timing adjustment value that is shorter than a superslot duration. Wherein a main superslot timing offset the A sub superslot timing offset The method of claim 14 which is encoded as part of a single coded value. The method of claim 14, wherein the main superslot timing offset and the sub superslot timing offset are encoded as two separate values.   The method of claim 1, wherein the base station is a satellite base station, and the access probe signal and the transmitted reply are OFDM signals. A base station using a periodic downlink timing structure in which beacon time slots occur on a periodic basis, wherein each beacon time slot includes a plurality of superslots representing continuous OFDM symbol transmission time intervals, A slot can be identified by using a superslot indicator, each superslot includes a plurality of symbol transmission periods, and the base station
A receiver module for receiving and detecting an access probe signal from a wireless terminal;
A transmitter module for transmitting a reply including information in response to the access probe signal;
The information is i) an integer multiple of a superslot period, the indicated main superslot timing offset correction amount, ii) in a beacon slot that is a period during which the base station receives an access probe signal corresponding to the reply A superslot identifier indicating the position of the superslot, iii) an identifier identifying the communication device that has transmitted the access probe signal corresponding to the reply, and iv) an identifier identifying the access probe corresponding to the reply. shows and,
The receiver module recognizes only access probe signals received within an access interval window, and accepts access probe signals outside the access interval window as interference noise .   The receiver module includes means for detecting reception of an access probe during a predetermined periodic period, wherein at least one of the predetermined periodic periods is at least one supermarket in each beacon slot. The base station according to claim 18, which occurs during a portion of a slot period, wherein the portion is less than half of a superslot duration.   The base station according to claim 18, further comprising means for transmitting at least one beacon signal during each beacon slot.   The base station according to claim 20, wherein the beacon signal is a single tone signal.   The base station according to claim 21, wherein the beacon signal has a duration shorter than three OFDM transmission periods. 19. The encoding module according to claim 18, further comprising an encoding module that includes, in the transmitted reply signal, a superslot identifier indicating a position of the superslot in a beacon slot that is a period in which the base station receives an access probe signal. base station. Further comprising an encoding module for encoding sub-superslot uplink timing correction information in the reply,
The base station according to claim 18, wherein the sub- super slot uplink timing correction information indicates a timing adjustment value shorter than a super slot duration. The received access probe signal includes a communication device identifier;
25. The base station of claim 24, further comprising a decoding module that decodes the received access probe signal to recover the encoded communication device identifier. The received access probe signal includes an encoded downlink superslot identifier;
The base station further includes:
A decoding module that decodes the received access probe signal to recover the encoded superslot identifier;
The main superslot timing offset that is an integral multiple of the superslot duration from the difference between the superslot index in the beacon slot of the superslot that is the period in which the access probe signal is received and the decoded superslot identifier A timing correction amount determination module for determining a correction amount ;
The base station according to claim 18 , wherein the periodic downlink timing structure is known by transmitting a downlink signal including a downlink beacon signal for each beacon slot .

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